[1] RUSSIAN ACAD SCI,INST ASTRON,MOSCOW,RUSSIA
[2] UNIV TEXAS,DEPT ASTRON,AUSTIN,TX 78712
[3] COPENHAGEN UNIV OBSERV,DK-1350 COPENHAGEN K,DENMARK
[4] NORDITA,DK-2100 COPENHAGEN 0,DENMARK
[5] PN LEBEDEV PHYS INST,MOSCOW,RUSSIA
[6] UNIV ILLINOIS,DEPT PHYS,URBANA,IL 61801