[1] NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA
[2] CALTECH, JET PROP LAB, PASADENA, CA 91103 USA
[3] WESTERN KENTUCKY UNIV, DEPT PHYS & ASTRON, BOWLING GREEN, KY 42101 USA
[4] UNIV MILAN, IST FIS, I-20133 MILAN, ITALY
[5] UNIV TORONTO, SCARBOROUGH COLL, TORONTO M5S 1A1, ONTARIO, CANADA
[6] EUROPEAN SPACE AGCY, SATELLITE TRACKING STN, MADRID, SPAIN
[7] SRC, APPLETON LAB, SLOUGH, BERKSHIRE, ENGLAND
[8] COMP SCI CORP, SILVER SPRING, MD 20900 USA
[9] APPLETON LAB, DIV ASTROPHYS RES, CULHAM, OXFORDSHIRE, ENGLAND
[10] UNIV FLORIDA, GAINESVILLE, FL 32720 USA
[11] OSSERVATORIO ASTRON, PADOVA, ITALY
[12] STOCKHOLM OBSERV, STOCKHOLM, SWEDEN
[13] EUROPEAN SO OBSERV, GENEVA, SWITZERLAND
[14] DEPT THEORET PHYS, OXFORD, ENGLAND
[15] CARNEGIE INST WASHINGTON, CALTECH, HALE OBSERV, WASHINGTON, DC 20005 USA