Author affiliations
1 University of Bologna and INFN Bologna, Via Irnerio 46, 40126 Bologna, Italy
2 Sky & Telescope, 49 Bay State Road, Cambridge, MA 02138-1200, USA
3 Department of Physics and Astronomy, Laurentian University, Sudbury, Ont. P3E 2C6, Canada
4 Department of Physics, Miyagi University of Education, Sendai, Miyagi 980-0845, Japan
5 IFSI-CNR Torino, University of Torino and INFN Torino, Via P Giuria 1, 10125 Torino, Italy
6 Department of Physics, University of Minnesota, Duluth, MN 55812-2496, USA
7 Los Alamos National Laboratory, Los Alamos, NM 87545, USA
8 Department of Physics, Queen's University, Kingston, Ont. K7L 3N6, Canada
9 Department of Physics, Boston University, Boston, MA 02215, USA
10 Institute for Cosmic Ray Research, University of Tokyo, Kashiwa, Chiba 277-8582, Japan
11 Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
12 Brookhaven National Laboratory, PO Box 5000, Upton, NY 11973-5000, USA
13 Current address: Department of Physics, University of California, Santa Barbara, CA 93106, USA.
14 Author to whom all correspondence should be addressed.
15 Current address: Department of Physics, University of Toronto, Toronto, Ont. M5S 1A7, Canada.