69 Universitaets-Sternwarte, Goettingen, Federal Republic of Germany 55 Cornell Univ., Ithaca, NY 50 Yerkes Observatory, Williams Bay, Wis. 48 Wisconsin Univ., Madison 46 Saint Andrews, University, Scotland 36 Lowell Observatory, Flagstaff, Ariz. 30 Lowell Observatory, Flagstaff, AZ, US 30 David Dunlap Observatory 26 Liege, Universite, Liege, Belgium 24 St. Andrews, University, St. Andrews, Scotland 23 Alabama, University, University, AL 21 St. Andrews, University, Scotland 19 Bochum, Ruhr-Univ., Germany 18 Millimeter Wave Observatory 17 Dartmouth College, Hanover, NH, US 16 Universitat de Barcelona, Barcelona, Spain 16 ST Systems Corp., Lanham, MD 16 Planetary Science Institute, Tucson, AZ 16 Observatoire de Geneve, Sauverny, Switzerland 16 Niels Bohr Institute, Copenhagen, Denmark 16 Lockheed Palo Alto Research Laboratory, Palo Alto, CA, US 16 Imperial College of Science, Technology, and Medicine, London, England 16 Fonds National de la Recherche Scientifique, Brussels, Belgium 15 Universidad de Cantabria, Santander, Spain 15 Tokyo Institute of Technology, Tokyo, Japan 15 Strasbourg, Observatoire Astronomique, France 15 Sachs/Freeman Associates, Inc., Bowie, MD 15 NASA, Ames Research Center, Theoretical and Planetary Studies Branch, Moffett Field, Calif. 15 NASA, Ames Research Center 15 Ministerio de Educacion de Chile, Santiago, Chile 15 Middle East Technical University, Ankara, Turkey 15 Instituto Argentino de Radioastronomia, Villa Elisa 15 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA 15 Fraunhofer Institut, Freiburg im Breisgau, West Germany 15 European Southern Observatory, Santiago de Chile, Chile 15 College of the Holy Cross, Worcester, MA 15 Ball Aerospace Systems Group, Boulder, CO 15 Astrophysikalisches Institut Potsdam, Potsdam, Germany 15 Akademiia Nauk SSSR, Institut Prikladnoi Matematiki, Moscow, USSR 15 AN SSSR, Fiziko-Tekhnicheskii Institut, Leningrad, USSR 14 University of Bristol, Bristol, UK 14 Universidade de Sao Paulo, Sao Paulo, Brazil 14 Univ. de Sao Paulo, Sao Paulo, Brazil 14 Sterrewacht Leiden, Postbus 9513, 2300 RA Leiden, The Netherlands 14 Radio Astronomy Observatory, Ann Arbor, MI 14 Palomar Observatory, California Inst. of Technology, Pasadena, CA, US 14 Molecular Research Institute, Palo Alto, CA 14 Max-Planck-Institut fuer Radioastronomie 14 Magyar Tudomanyos Akademia, Kozponti Fizikai Kutato Intezet, Budapest, Hungary 14 MPI fuer Extraterrestrische Physik, Garching, Germany 14 Leander McCormick Observatory, Charlottesville, VA 14 Kiepenheuer-Inst. fuer Sonnenphysik, Freiburg, Germany 14 Kernforschungszentrum Karlsruhe GmbH, Federal Republic of Germany 14 Instituto Nacional de Astrofisica, Optica y Electronica, Puebla, Mexico 14 Institut de Radio Astronomie Millimetrique, Grenoble, France 14 Hughes STX Corp., Lanham, MD 14 Department of Physics, University of Durham, South Road, Durham DH1 3LE, UK 14 Commissariat a l'Energie Atomique, Service d'Astrophysique, Gif-sur-Yvette, Essonne, France 14 Athens, National Capodistrian University, Greece 14 Astrophysics, Department of Physics, Keble Road, Oxford OX1 3RH, UK 14 Akademiia Nauk SSSR, Fiziko-Tekhnicheskii Institut, Leningrad, USSR 13 University of Nigeria, Nsukka 13 University of New Hampshire, Durham, NH, US 13 Universidad de Puerto Rico, Rio Piedras 13 Universidad Complutense, Madrid, Spain 13 Universidad Central de Venezuela, Caracas 13 Universidad Autonoma de Madrid, Madrid, Spain 13 Univ. of Helsinki, Helsinki, Finland 13 U.S. Naval Observatory 13 Netherlands Foundation for Research in Astronomy, Dwingeloo 13 National Research Council of Canada, Ottawa, Ontario, Canada 13 NASA, Goddard Space Flight Center, Theoretical Studies Group, Greenbelt, Md. 13 NASA, Astrophysics Div., Washington, DC 13 Mount John University Observatory, Christchurch, New Zealand 13 Missouri, University, Saint Louis 13 Max-Planck-Inst. fuer Aeronomie, Katlenburg-Lindau, Germany 13 Leander McCormick Observatory, Charlottesville, Va. 13 Instituto Nacional de Tecnica Aeroespacial, Torrejon de Ardoz, Spain 13 Indiana University, Bloomington, IN, US 13 Hughes STX Corp., Greenbelt, MD 13 Embry-Riddle Aeronautical University, Daytona Beach, FL 13 Dipartimento di Astronomia, Universita di Padova, vicolo dell'Osservatorio 5, I-35122 Padova, Italy 13 Czech Academy of Sciences, Astronomical Inst., Ondrejov, Czech Republic 13 Copenhagen University Observatory, Tollose, Denmark 13 China Center for Advanced Science and Technology, Beijing 13 CNRS/UPS, Toulouse, France 13 Biurakanskaia Astrofizicheskaia Observatoriia, Yerevan, Armenian SSR 13 Arcetri, Osservatorio Astrofisico 12 Villanova University, Villanova, PA, US 12 University of Pittsburgh, Pittsburgh, PA, US 12 University of Oxford, Department of Physics, Nuclear Physics Laboratory, Keble Road, Oxford OX1 3RH, UK 12 University of New Mexico, Albuquerque, NM, US 12 University of Kansas, Lawrence, KS, US 12 University of Calgary, Calgary, Alberta, Canada 12 Universita di Firenze, Firenze, Italy 12 Univ. of Victoria, Victoria, BC, Canada 12 Univ. of Manchester Inst. of Science and Technology, United Kingdom 12 Tromso, Universitetet, Tromso, Norway 12 Royal Australian Air Force Academy, Melbourne, Australia 12 Potchefstroom Univ., Potchefstroom, South Africa 12 Osservatorio Astronomico di Bologna, via Zamboni 33, I-40126 Bologna, Italy 12 New Brunswick, University, Fredericton, Canada 12 NSF, Div. of Astronomical Sciences, Washington, DC 12 NASA, Goddard Space Flight Center, Laboratory for Optical Astronomy, Greenbelt, Md. 12 Mission Research Corp., Albuquerque, NM 12 Institute for Molecular Science, Okazaki, Japan 12 Institut za Fiziku, Belgrade, Yugoslavia 12 Inst. Astronomico e Geofisico, Sao Paulo, Brazil 12 Imperial College of Science, Technology, and Medicine, London, United Kingdom 12 Houston Baptist University, Houston, Tex. 12 Hartebeesthoek Radio Astronomy Observatory, Krugersdorp, Republic of South Africa 12 Georgia State University, Atlanta, Ga. 12 Frankfurt, Universitaet, Frankfurt am Main, West Germany 12 Department of Pure and Applied Physics, The Queen's University of Belfast, Belfast BT7 1NN, UK 12 Department of Physics and Astronomy, University of Wales, Cardiff CF2 3YB, UK 12 Cincinnati, University, Cincinnati, OH 12 Centre d'Etudes et de Recherches de la Machine-Outil, Saint-Martin-d'Heres, France 12 Center for Particle Astrophysics, University of California, Berkeley, CA 94720, USA 12 Cape Town Univ., Rondebosch, South Africa 12 CEA, Centre d'Etudes de Bruyeres-le-Chatel, France 12 Antwerpen, Rijksuniversitair Centrum, Antwerp, Belgium 12 AN SSSR, Institut Iadernykh Issledovanii, Moscow, USSR 11 University of Alabama, Tuscaloosa, AL, US 11 Universite de Liege, Liege, Belgium 11 Universita di Bologna, Bologna, Italy 11 Universidad de Puerto Rico, Rio Piedras, PR 11 Univ. of Western Ontario, London, Ontario, Canada 11 Univ. of Science and Technology of China, Hefei 11 Univ. of North Carolina, Chapel Hill, NC, US 11 Univ. of Lund, Lund, Sweden 11 Torun, Uniwersytet, Torun, Poland 11 The Queen's University of Belfast, Belfast, UK 11 Tata Institute of Fundamental Research, Udhagamandalam, India 11 Science Research Council, Rutherford and Appleton Laboratories, Didcot, Oxon, England 11 Science Research Council, Appleton Laboratory, Abingdon, Oxon, England 11 San Francisco State University, CA 11 Research Centre for Theoretical Astrophysics, University of Sydney, NSW 2006, Australia 11 Natsionalna Astronomicheska Observatoriia, Sofia, Bulgaria 11 Maria Mitchell Observatory, Nantucket, MA, US 11 London, University College, Mullard Space Science Laboratory, Dorking, Surrey, England 11 Lockheed Palo Alto Research Lab., Palo Alto, CA, US 11 Liege, Universite, Cointe-Ougree 11 Liege, Institut d'Astrophysique, Belgium 11 Lawrence Berkeley Laboratory 11 INPE, Sao Jose dos Campos, Brazil 11 IBM Almaden Research Center, San Jose, CA 11 ETH-Zentrum, Zurich, Switzerland 11 Department of Physics, University of Durham, South Road, Durham DH1 3LE 11 Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH, UK 11 Darmstadt, Technische Hochschule, Darmstadt, West Germany 11 Crimean Astrophysical Observatory, Nauchny, Ukraine 11 Corralitos Observatory, Las Cruces, NM 11 Cavendish Laboratory, Madingley Road, Cambridge CB3 0HE, UK 11 CSIRO, Epping, Australia 11 CNR, Istituto di Fisica Cosmica e Informatica, Palermo, Italy 11 Bowling Green State University, Bowling Green, Ohio 11 Bhabha Atomic Research Centre, Srinagar, India 11 Beijing Astronomical Observatory, China 11 Atomic Energy Research Establishment, Culham Laboratory, Abingdon, Oxon, England 11 Aix-Marseille I, Universite, Marseille, France 11 Aichi University of Education, Kariya, Japan 10 Wyzsza Szkola Pedagogiczna, Opole, Poland 10 Vatican Observatory, Vatican City State 10 Vassar College Observatory, Poughkeepsie, NY 10 University of Utah, Salt Lake City, UT, US 10 University of Durham, Durham, UK 10 Univ. of Utah, Salt Lake City, UT, US 10 Univ. of Thessaloniki, Thessaloniki, Greece 10 Univ. of Bern, Bern, Switzerland 10 Univ. de Valencia, Valencia, Spain 10 Tokyo Metropolitan University, Japan 10 The Queen's Univ. of Belfast, Belfast, Northern Ireland 10 State Astronomical Inst., Moscow, Russia 10 Specola Vaticana, Castel Gandolfo, Vatican City State 10 ST Systems Corp., Greenbelt, MD 10 SRON, Laboratorium voor Ruimteonderzoek 10 Rikkyo Univ., Toshima, Tokyo, Japan 10 Rhodes University, Grahamstown, Republic of South Africa 10 Queen's Univ. of Belfast, Belfast, N. Ireland, UK 10 Osmania University, Hyderabad, India 10 Nicolaus Copernicus Astronomical Center, Warsaw, Poland 10 NASA, Langley Research Center, Hampton, Va. 10 Muenchen, Univ., Munich, Germany 10 Missouri-Saint Louis, University, Saint Louis 10 Max-Planck-Inst. fuer extraterrestrische Physik, Germany 10 Leiden Southern Station, Broederstroom, Republic of South Africa 10 Kernforschungszentrum Karlsruhe GmbH, Karlsruhe, West Germany 10 Istituto Universitario Navale, Naples, Italy 10 International Centre for Relativistic Astrophysics, Rome, Italy 10 International Centre for Relativistic Astrophysics 10 International Center for Relativistic Astrophysics, Rome, Italy 10 Institute of Space and Astronautical Science, 3-1-1 Yoshinodai, Sagamihara, Kanagawa 229, Japan 10 Inst. d'Astrophysique Spatiale, Orsay, France 10 Haystack Observatory, Westford, Mass. 10 Flower and Cook Observatory, Philadelphia, Pa. 10 Division of Physical Sciences, University of Hertfordshire, College Lane, Hatfield, Herts AL10 9AB, UK 10 Department of Physics and Astronomy, University of Wales College of Cardiff, PO Box 913, Cardiff CF2 3YB, UK 10 Department of Physics and Astronomy, Northwestern University, Evanston, IL 60208, USA 10 Cooperative Institute for Research in Environmental Sciences, Boulder, CO 10 Commissariat al'Energie Atomique, Service d'Astrophysique, Gif-sur-Yvette, Essonne, France 10 Cataluna, Universidad Politecnica, Barcelona, Spain 10 Braeside Observatory, Flagstaff, AZ 10 Astrophysikalisches Inst. Potsdam, Potsdam, Germany 10 American Association of Variable Star Observers, Cambridge, MA 10 Aarhus Universitet, Aarhus, Denmark 10 AN SSSR, Institut Prikladnoi Matematiki, Moscow, USSR 9 Villanova Univ., Villanova, PA, US 9 University of Oxford, Nuclear and Astrophysics Laboratory, Keble Road, Oxford OX1 3RH, UK 9 University of Leicester, Leicester, UK 9 Universita di Catania, Catania, Italy 9 Univ. of Waikato, Hamilton, New Zealand 9 Univ. of New Hampshire, Durham, NH, US 9 Univ. Joseph Fourier, Grenoble, France 9 U.S. Naval Academy, Annapolis, MD 9 Sternberg Astronomical Institute, Moscow, Russia 9 Southwest Research Institute, San Antonio, TX 9 School of Physics, University of Sydney, NSW 2006, Australia 9 San Diego State University, San Diego, Calif. 9 Sachs/Freeman Associates, Inc., Landover, MD 9 Radio Astronomy Observatory, Ann Arbor, Mich. 9 Observatorio Astronomico, Santiago de Compostela, Spain 9 Observatoire du Pic-du-Midi, Bagneres-de-Bigorre, France 9 Northern Arizona University, Flagstaff, AZ 9 North Carolina State Univ., Raleigh, NC, US 9 NSF Center for Particle Astrophysics, US 9 Middle East Technical Univ., Ankara, Turkey 9 McDonald Observatory, Texas Univ., Austin, TX, US 9 Kapteyn Sterrenwacht, Roden, Netherlands 9 Ist. Nazionale di Fisica Nucleare, Italy 9 Interferometrics, Inc., Vienna, VA 9 Inter-Univ. Centre for Astronomy and Astrophysics, Poona, India 9 Instituto Astronomico e Geofisico, Sao Paulo, Brazil 9 Institute for Astronomy, University of Edinburgh, Blackford Hill, Edinburgh EH9 3HJ, UK 9 European Southern Observatory 9 Edinburgh, Royal Observatory, U.K. Schmidt Telescope Unit, Coonabarabran, New South Wales, Australia 9 Department of Physics and Astronomy, University of Wales College of Cardiff, PO Box 913, Cardiff CF2 3YB 9 Department of Physics and Astronomy, Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218, USA 9 Department of Astronomy, University of Texas, Austin, TX 78712, USA 9 DAPNIA, Gif-sur-Yvette, France 9 Commissariat a l'Energie Atomique, Section d'Astrophysique, Gif-sur-Yvette, Essonne, France 9 Clyde W. Tombaugh Observatory, Lawrence, KS 9 Centre d'Etudes et de Recherches Geodynamiques et Astronomiques, Grasse, France 9 California Association for Research in Astronomy, Kamuela, HI, US 9 CNRS, Institut d'Astrophysique Spatiale, Verrieres-le-Buisson, France 9 CEN de Saclay, Gif-sur-Yvette, France 9 Beijing Astronomical Observatory, Beijing, China 9 Australian Defence Force Academy, Campbell, Australia 9 Astronomy Unit, Queen Mary and Westfield College, University of London, Mile End Road, London E1 4NS, UK 9 Astronomy Centre, University of Sussex, Falmer, Brighton BN1 9QH 9 Astrofizicheskaia Observatoriia, Tartu, Estonian SSR 9 Applied Research Corp., Greenbelt, MD 8 Vassar College, Poughkeepsie, NY 8 University of Victoria, Victoria, BC, Canada 8 University of Manchester, NRAL, Jodrell Bank, Macclesfield, Cheshire SK11 9DL, UK 8 University of Birmingham, Edgbaston, Birmingham, UK 8 University of Alabama at Huntsville, Huntsville, AL, US 8 Universite Paris-Sud, Orsay, France 8 Universita di Milano, Milano, Italy 8 Universidade Mackenzie, Sao Paulo, Brazil 8 Univ. of Pittsburgh, Pittsburgh, PA, US 8 Univ. of New Mexico, Albuquerque, NM, US 8 Univ. de Cantabria, Santander, Spain 8 Univ. de Barcelona, Barcelona, Spain 8 Tartuskaia Astrofizicheskaia Observatoriia, Toravere, Estonian SSR 8 Swarthmore College, Swarthmore, PA 8 Steward Observatory, University of Arizona, Tucson, AZ 85721, USA 8 Sterrenkundig Observatorium, Ghent, Belgium 8 Sternwarte der Universitaet Bonn, Bonn, Germany 8 Space Telescope European Coordinating Facility, Garching, Germany 8 Sonnenobservatorium Kanzelhoehe, Sattendorf, Austria 8 Societat Catalana de Fisica, Spain 8 San Diego State University, San Diego, CA, US 8 San Diego State Univ., San Diego, CA, US 8 SISSA/ISAS, Trieste, Italy 8 Ruhr-Universitat Bochum, Bochum, Germany 8 Rosemary Hill Observatory, Gainesville, FL 8 Rio de Janeiro, Observatorio Nacional, Rio de Janeiro, Brazil 8 Physics Department, University of Tasmania, GPO Box 252C, Hobart, TAS 7001, Australia 8 Palomar Observatory, California Inst. of Tech., Pasadena, CA, US 8 Observatorio del Roque de los Muchachos, Santa Cruz de la Palma, Spain 8 Nicolaus Copernicus Astronomical Center, Bartycka 18, 00-716 Warsaw, Poland 8 Nauchno-Issledovatel'skii Radiofizicheskii Institut, Gorki, USSR 8 NRAO, Charlottesville, VA, US 8 NASA, Marshall Space Flight Center 8 NASA, Goddard Space Flight Center, Laboratory for Planetary Atmospheres, Greenbelt, MD 8 Mt Stromlo and Siding Spring Observatories, Australian National University, Weston, ACT 2611, Australia 8 Monterey Institute for Research in Astronomy, CA 8 Max-Planck-Institut fuer Physik und Astrophysik, Garching 8 Mathematical Science Consultants, Inc., Greenbelt, MD 8 MPI fuer Astronomie, Heidelberg, Germany 8 MIT Haystack Observatory, Westford, MA, US 8 Lockheed Missiles and Space Co., Inc., Palo Alto, Calif. 8 Leiden Observatory, PO Box 9513, 2300 RA Leiden, The Netherlands 8 Karlova Universita, Prague, Czechoslovakia 8 Joint Astronomy Centre, 660 N. A`ohoku Place, Hilo, HI 96720, USA 8 Instituto de Astrofisica de Canarias, Tenerife, Canary Islands, Spain 8 Instituto Argentino de Radioastronomia, Villa Elisa, Buenos Aires, Argentina 8 IRAM, St. Martin d'Heres, France 8 Hughes STX, Lanham, MD, US 8 Helsinki University of Technology, Espoo, Finland 8 Haystack Observatory, Westford, MA, US 8 Harvard College Observatory, Cambridge, Mass. 8 Hartebeesthoek Radio Astronomy Observatory, Krugersdorp, South Africa 8 Grenoble I, Universite, Saint-Martin-d'Heres, Isere, France 8 Grenoble I, Universite, Grenoble, France 8 Goteborg, Universitet, Sweden 8 General Sciences Corp., Laurel, MD 8 Dublin Institute for Advanced Studies, Republic of Ireland 8 Division of Physical Sciences, University of Hertfordshire, Hatfield, Herts AL10 9AB, UK 8 Division of Physical Sciences, University of Hertfordshire, Hatfield, Hertfordshire AL10 9AB, UK 8 Department of Physics, University of Oxford, Keble Road, Oxford OX1 3RH, UK 8 Department of Physics, University College, The University of New South Wales, Australian Defence Force Academy, Canberra, ACT 2600, Australia 8 Department of Physics and Astronomy, Arizona State University, Tempe, AZ 85287-1504, USA 8 Copenhagen, University, Denmark 8 Commonwealth Scientific and Industrial Research Organization, Epping, New South Wales, Australia 8 Colorado College, Colorado Springs 8 China Center for Advanced Science and Technology 8 Chilbolton Observatory, Stockbridge, Hants., England 8 Chalmers University of Technology, Goteborg, Sweden 8 CONICET, Buenos Aires, Argentina 8 CNRS, Centre de Spectrometrie Nucleaire et de Spectrometrie de Masse, Orsay, Essonne, France 8 CNR, Ist. di Studio e Tecnologie sulle Radiazioni Extraterrestri, Bologna, Italy 8 CESR-CNRS/UPS, Toulouse, France 8 Braeside Observatory, Flagstaff, AZ, US 8 Bowling Green State University, OH 8 Bosscha Observatory, Lembang, Indonesia 8 Beograd, Univerzitet, Belgrade, Yugoslavia 8 Barcelona, Universidad Central, Barcelona, Spain 8 Astrophysikalisches Institut Potsdam, An der Sternwarte 16, D-14482 Potsdam, Germany 8 Amherst College, Amherst, Mass. 8 Akademiia Nauk SSSR, Institut Zemnogo Magnetizma, Ionosfery i Rasprostraneniia Radiovoln, Troitsk, USSR 8 Academy of Sciences of the Czech Republic, Czech Republic 7 Western Washington University, Bellingham, WA 7 University of South Africa, Pretoria, Republic of South Africa 7 University of California at Santa Barbara, Santa Barbara, CA, US 7 University College, Dublin, Republic of Ireland 7 Univ. of Crete, Heraklion, Greece 7 Univ. of Alabama in Huntsville, Huntsville, AL, US 7 Tokyo Inst. of Technology, Meguro, Tokyo, Japan 7 Stockholm, Universitet, Stockholm, Sweden 7 Special Astrophysical Observatory, Nizhni Arkhyz, Russia 7 South African Council for Scientific and Industrial Research, National Institute for Telecommunications Research, Johannesburg, Republic of South Africa 7 Service d'Astrophysique, France 7 Seoul National Univ., Seoul, Korea 7 Scientific and Technical Research Council of Turkey, Research Institute for Basic Sciences, Gebze 7 Scarborough College, West Hill, Ontario, Canada 7 San Fernando Observatory, Northridge, CA 7 Saint Andrews, University Observatory, Scotland 7 SRON, Laboratory for Space Research, Groningen, Netherlands 7 Rosemary Hill Observatory, Gainesville, Fla. 7 Radio Astronomy Observatory, Austin, Tex. 7 Quebec, Observatoire Astronomique, Quebec, Canada 7 Planetary Science Inst., Tucson, AZ 7 Perth Observatory, Bickley, Australia 7 Observatorio Nacional, Sao Paulo, Brazil 7 Netherlands Foundation for Research in Astronomy, Dwingeloo, Netherlands 7 Netherlands Foundation for Radio Astronomy, Dwingeloo, Netherlands 7 National Institute of Standards and Technology, Boulder, CO, US 7 National Center for Supercomputing Applications, Urbana, IL, US 7 Natal, University, Durban, Republic of South Africa 7 NSF, Center for Particle Astrophysics, Berkeley 7 NASA, Ames Research Center, Theoretical and Planetary Studies Branch, Moffett Field, CA 7 Max-Planck-Institut fuer Aeronomie, Katlenburg-Lindau, West Germany 7 Max-Planck-Inst. fuer extraterrestrische Physik, Muenchen, Germany 7 Max-Planck-Inst. fuer Extraterrestrische Physik, Germany 7 Lockheed Missiles and Space Co., Inc., Palo Alto, CA 7 Lawrence Berkeley Laboratory, Berkeley, CA, US 7 Laboratorium voor Ruimteonderzoek 7 Lab. for Space Research 7 Kawasaki Heavy Industries, Ltd., Aircraft Engineering Div., Kakamigahara, Japan 7 Katholieke Univ. Leuven, Heverlee, Belgium 7 Karl-Schwarzschild-Observatorium, Tautenburg, Germany 7 Kapteyn Astronomical Institute, PO Box 800, 9700 AV Groningen, The Netherlands 7 Kapteyn Astronomical Institute, Groningen, Netherlands 7 Inter-University Centre for Astronomy and Astrophysics, Post Bag 4, Ganeshkhind, Pune 411007, India 7 Institute of Astronomy, Zurich, Switzerland 7 Institute of Astronomy, Cambridge University, Madingley Road, Cambridge CB3 0HA, UK 7 Inst. of Solar-Terrestrial Physics, Russia 7 Hungarian Academy of Sciences, Budapest, Hungary 7 Herzberg Institute of Astrophysics, Victoria, BC, Canada 7 Hatfield Polytechnic Observatory, Hertford, Herts., England 7 Hartebeesthoek Radio Astronomy Observatory, PO Box 443, Krugersdorp 1740, South Africa 7 Goettingen, Univ.-Sternwarte, Germany 7 Glavnaia Astronomicheskaia Observatoriia, Pulkovo, USSR 7 Frankfurt, Universitaet, Frankfurt am Main, Federal Republic of Germany 7 Florida Atlantic University, Boca Raton 7 European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching bei Munchen, Germany 7 Dublin Institute for Advanced Studies, Ireland 7 Department of Physics and Astronomy, University of Wales, College of Cardiff, PO Box 913, Cardiff CF2 3YB 7 Department of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK 7 Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA 70803-4001, USA 7 Department of Astronomy and McDonald Observatory, University of Texas, Austin, TX 78712, USA 7 Departamento de Astronomia y Astrofisica, Universidad de Valencia, Dr. Moliner 50, E-46100 Burjassot, Valencia, Spain 7 Danish Space Research Institute, Lyngby, Denmark 7 Danish Space Research Inst., Lyngby, Denmark 7 Crimean Astrophysical Observatory, Crimea, Ukraine 7 Copernicus Astronomical Center, Warsaw, Poland 7 Complejo Astronomico El Leoncito, San Juan, Argentina 7 Commissariat a l'Energie Atomique, Service d'Electronique Physique, Gif-sur-Yvette, Essonne, France 7 Clark Lake Radio Observatory, Borrego Springs, CA 7 Center for Solar and Space Research, Yale Univ., New Haven, CT, US 7 California, University, Lawrence Berkeley Laboratory, Berkeley, Calif. 7 California, University, Berkeley and Livermore 7 CNRS, Laboratoire Rene Bernas, Orsay, France 7 CNRS, Inst. d'Astrophysique 7 CNR, Istituto per le Applicazioni Interdisciplinari della Fisica, Palermo, Italy 7 Bulgarian Academy of Sciences, Dept. of Astronomy, Sofia, Bulgaria 7 Brockport State College, Brockport, NY 7 Berkeley Research Associates, CA 7 Astronomy Unit, School of Mathematical Sciences, Queen Mary and Westfield College, Mile End Road, London E1 4NS 7 Aerospace Corp., Space and Environment Technology Center, Los Angeles, CA 7 APS Division, Department of Pure and Applied Physics, Queen's University, Belfast BT7 1NN, UK 6 Wollongong, University, Australia 6 Wesleyan University, Middletown, CT, US 6 University of Oxford, Department of Astrophysics, Nuclear Physics Building, Keble Road, Oxford OX1 3RH, UK 6 University of Illinois, Urbana, Illinois, US 6 Universitat Wurzburg, Wurzburg, Germany 6 Universitat Munchen, Munchen, Germany 6 Universidad Nacional de La Plata, La Plata, Argentina 6 Universidad Complutense de Madrid, Madrid, Spain 6 Univ. of Turku, Piikkio, Finland 6 Univ. of Groningen, Groningen, Netherlands 6 Univ. of Central Lancashire, Preston, UK 6 Univ. of Adelaide, Adelaide, Australia 6 Univ. de Liege, Liege, Belgium 6 USAF, Phillips Laboratory, Hanscom AFB, MA 6 URA 1361 du CNRS, Saint-Vallier, France 6 UCO/Lick Observatory, University of California, Santa Cruz, CA 95064, USA 6 Toronto, University, Mississauga, Canada 6 Tohoku Univ., Aoba, Sendai, Japan 6 The Wise Observatory and the School of Physics and Astronomy, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 69978, Israel 6 Swarthmore College, Swarthmore, Pa. 6 Sterrewacht Leiden, PO Box 9513, 2300 RA Leiden, The Netherlands 6 Southwestern 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Hautes-Pyrenees 6 Physics Department, University of Tasmania, GPO Box 252C, Hobart, Tasmania, Australia 7001 6 Physics Department, The University of Queensland, Queensland 4072, Australia 6 Paul Wild Observatory, Narrabri, Australia 6 Osservatorio Astronomico, Via Zamboni 33, I-40126 Bologna, Italy 6 Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, I-50125 Firenze, Italy 6 Northern Arizona Univ., Flagstaff, AZ 6 Nordlyobservatoriet, Tromso, Norway 6 Nijmegen, Katholieke Universiteit, Nijmegen, Netherlands 6 National Bureau of Standards, Laboratory Astrophysics Div., Boulder, Colo. 6 National Air and Space Museum, Washington, DC 6 Nagoya University, Chikusa-ku, Nagoya, Japan 6 NASA, Johnson Space Center, Astrophysics Section, Houston, Tex. 6 Muenchen, Universitaet, Munich 6 Mount Stromlo and Siding Spring Observatories 6 Metsahovi Radio Research Station, Kylmala, Finland 6 Max-Planck-Institute, Garching, Germany 6 Max-Planck-Institut fur Astrophysik, Postfach 1523, D-85740 Garching, Germany 6 Main Astronomical Observatory, Goloseevo, Ukraine 6 Lockheed Solar and Astrophysics Laboratory, Palo Alto, CA, US 6 Lewis and Clark College, Portland, OR, US 6 Lab. d'Astrophysique de Toulouse, Toulouse, France 6 Kiepenheuer-Institut fuer Sonnenphysik, Freiburg, Germany 6 Istituto Universitario Navale 6 Istituto Nazionale di Fisica Nucleare, Padua, Italy 6 Ist. 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Building, Hounsfield Road, Sheffield S3 7RH, UK 6 Department of Physics, The Citadel, Charleston, SC 29409, USA 6 Department of Physics, Science Laboratories, South Road, Durham DH1 3LE, UK 6 Department of Physics and Astronomy, University of Manchester, Schuster Laboratory, Oxford Road, Manchester M13 9PL, UK 6 Department of Physics and Astronomy, University of Manchester, Schuster Laboratory, Oxford Road, Manchester M13 9PL 6 Department of Physical Sciences, University of Hertfordshire, College Lane, Hatfield, Herts AL10 9AB 6 Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge CB3 9EW 6 Cornell University, Ithaca, New York, US 6 Computer Sciences Corp., Astronomy Dept., Silver Spring, MD 6 Communications Research Laboratory, Tokyo, Japan 6 Commonwealth Scientific and Industrial Research Organization, Div. of Chemical Physics, Clayton, Victoria, Australia 6 Clark Lake Radio Observatory, Borrego Springs, Calif. 6 City Polytechnic of Hong Kong, Kowloon 6 Charles Univ., Prague, Czech Republic 6 Centre d'Etudes et de Recherches de la Machine-Outil, Saint-Martin-d'Heres, Isere, France 6 Centre d'Etudes et de Recherches Geodynamiques et Astronomiques, Saint-Vallier-de-Thiey, Alpes-Maritimes, France 6 Carnegie Observatories, 813 Santa Barbara Street, Pasadena, CA 91101, USA 6 California State University, San Bernardino 6 California Institute of Technology, Jet Propulsion Laboratory 6 CNRS, Centre de Spectrometrie Nucleaire et de Spectrometrie de Masse, Orsay, France 6 CNR, Istituto di Fisica Cosmica ed Applicazioni dell'Informatica, Palermo, Italy 6 CNR, Ist. di Fisica Cosmica con Applicazioni all'Informatica, Palermo, Italy 6 CNR, Centro per l'Astronomia Infrarossa, Florence, Italy 6 Byurakan Astrophysical Observatory, Armenia 6 Bowling Green State University, Bowling Green, OH 6 Blackett Laboratory, Imperial College, London SW7 2BZ, UK 6 Biurakanskaia Astrofizicheskaia Observatoriia, Byurakan, Armenian SSR 6 Ball Brothers 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Zemnogo Magnetizma, Ionosfery i Rasprostraneniia Radiovoln, Troitsk, USSR 5 Wroclaw, Uniwersytet, Obserwatorium, Poland 5 Western Kentucky University, Bowling Green, Ky. 5 Western Kentucky University, Bowling Green, KY 5 Western Australia, University, Nedlands, Australia 5 Weber State College, Ogden, UT 5 University of Tokyo, Mitake-mura, Kiso-gun, Japan 5 University of Southampton, Department of Physics, Highfield, Southampton SO17 1BJ, UK 5 University of Notre Dame, Notre Dame, IN, US 5 University of Nigeria, Nsukka, Nigeria 5 University of Manchester, Cheshire, UK 5 University of Cape Town, Cape Town, South Africa 5 Universitat de les Illes Balears, Palma de Mallorca, Spain 5 Universitat Heidelberg, Heidelberg, Germany 5 Universidade Federal Fluminense, Niteroi, Brazil 5 Universidad de Valencia, Valencia, Spain 5 Univ. of Toronto, Mississauga, Ontario, Canada 5 Univ. of Tokyo, Meguro-ku, Tokyo, Japan 5 Univ. of Southampton, Southampton, UK 5 Univ. of Pennsylvania, Philadelphia, PA, US 5 Univ. of Electro-Communications, Tokyo, Japan 5 Univ. of Birmingham, Birmingham, UK 5 Univ. de les Illes Balears, Palma de Mallorca, Spain 5 Univ. Nacional de La Plata, La Plata, Argentina 5 Univ. Heidelberg, Heidelberg, Germany 5 USAF, Phillips Lab., Hanscom AFB, MA 5 U.S. Merchant Marine Academy, Kings Point, NY 5 Trenton State College, Trenton, N.J. 5 Tokyo Metropolitan Univ., Tokyo, Japan 5 Theoretical Physics, Department of Physics, 1 Keble Road, Oxford OX1 3NP 5 Systems and Applied Sciences Corp., Hyattsville, MD 5 Sussex Univ., Falmer, UK 5 Stichting Astronomisch Onderzoek in Nederland, Amsterdam, Netherlands 5 Stephen F. 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Argentino de Radioastronomia, Argentina 3 Insititute of Technology, Cambridge, MA, 02139 3 Indonesian National Institute of Aeronautics and Space, Djakarta, Indonesia 3 Indiana University, Bloomington, Indiana, US 3 Indian Institute of Astrophysics, Koramangala, Bangalore 560034, India 3 IZMIRAN, Troitsk, USSR 3 IPAC, California Institute of Technology, 770 South Wilson Avenue, Mail Code 100-22, Pasadena, CA 91125, USA 3 INFN - Sezione di Perugia, c/o Dipartimento di Fisica dell'Universita, via A. 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Ioffe Institute of Physics and Technology, St. Petersburg, Russia 2 A.F. Ioffe Institute for Physics and Technology, St. Petersburg, Russia 2 A. F. Ioffe Institute for Physics and Technology, 194021 St. Petersburg, Russia 2 6127 Wilder Laboratory, Department of Physics and Astronomy, Dartmouth College, Hanover NH 03755, USA 2 61 Rosebery Street, Bedford, 6052 Western Australia 2 1150 University Avenue, Space Astronomy Laboratory, University of Wisconsin, Madison, WI 53706, USA 1 {CNR - Istituto di Fisica Cosmica e Tecnologie Relative, Via Bassini 15, 20133 Milano, Italy and Dip. Fisica, Universita di Milano, Via Celoria 16, 20133 Milano, Italy 1 te 142, 4 place Jussieu, 75005 Paris, France 1 internet: zacs@acad.latnet.lv 1 and Visiting astronomer, Cerro Tololo Inter-American observatory, operated under contract No. AST 78-27879 1 and Universitatssternwarte Munchen, Scheinerstr. 1, D-81679 Munchen, Germany 1 and URA 173 (associee au CNRS et a l'Universite Paris 7) et DAEC, Observatoire de Paris, F-92195 Meudon, France 1 and Max--Planck--Institut fur Extraterrestrische Physik (MPE), Giessenbachstrasse, Postfach 1603, D-85740 Garching, Germany), AB- 1 and Istituto Nazionale di Ottica, Largo E. Fermi 6, I--50125 Firenze, Italy 1 and Dpto. 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