[1] Univ Chicago, Dept Astron & Astrophys, Chicago, IL 60637 USA
[2] Fermilab Natl Accelerator Lab, Batavia, IL 60510 USA
[3] Univ Washington, Dept Astron, Seattle, WA 98195 USA
[4] Princeton Univ Observ, Princeton, NJ 08544 USA
[5] Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA
[6] Univ Chicago, Yerkes Observ, Williams Bay, WI 53191 USA
[7] Apache Point Observ, Sunspot, NM 88349 USA
[8] CALTECH, Dept Astron, Pasadena, CA 91125 USA
[9] Observ Midi Pyrenees, F-31400 Toulouse, France
[10] Univ Pittsburgh, Dept Phys & Astron, Pittsburgh, PA 15260 USA
[11] Eotvos Lorand Univ, Dept Phys Complex Syst, H-1117 Budapest, Hungary
[12] Univ Tokyo, Dept Astron, Bunkyo Ku, Tokyo 1130033, Japan
[13] Univ Tokyo, Sch Sci, Res Ctr Early Universe, Bunkyo Ku, Tokyo 1130033, Japan
[14] Inst Adv Study, Princeton, NJ 08540 USA
[15] Yale Univ, Dept Phys, New Haven, CT 06520 USA
[16] Natl Astron Observ, Mitaka, Tokyo 1818588, Japan
[17] Univ Tokyo, Inst Cosm Ray Res, Tanashi, Tokyo 1888502, Japan
[18] USN Observ, Flagstaff Stn, Flagstaff, AZ 86002 USA
[19] USN Observ, Washington, DC 20392 USA
[20] USN, Res Lab, Remote Sensing Div, Washington, DC 20375 USA
[21] Observ Carnegie Inst Washington, Pasadena, CA 91101 USA
[22] Tohoku Univ, Inst Astron, Aoba Ku, Sendai, Miyagi 9808578, Japan
[23] Merrill Lynch Japan Inc, Tokyo 100, Japan
[24] Los Alamos Natl Lab, Los Alamos, NM 87545 USA
[25] Univ Michigan, Dept Phys, Ann Arbor, MI 48109 USA
[26] Royal Observ, Edinburgh EH9 3HJ, Midlothian, Scotland
[27] Carnegie Mellon Univ, Dept Phys, Pittsburgh, PA 15232 USA
[28] Rensselaer Polytech Inst, Dept Phys Appl Phys & Astron, Troy, NY 12180 USA
[29] Lucent Technol, Naperville, IL 60566 USA
[30] Osserv Astron Trieste, Div Astron & Astrofis, I-34131 Trieste, Italy
[31] Rochester Inst Technol, Dept Phys, Rochester, NY 14623 USA
[32] Penn State Univ, Dept Astron & Astrophys, University Pk, PA 16802 USA
[33] Univ Toronto, Canadian Inst Theoret Astrophys, Toronto, ON M5S 3H8, Canada
[34] Drexel Univ, Dept Phys, Philadelphia, PA 19104 USA
[35] Inst Space & Astronaut Sci, Sagamihara, Kanagawa 229, Japan
[36] Ohio State Univ, Dept Astron, Columbus, OH 43210 USA