[1] UNIV BRITISH COLUMBIA,PHYS DEPT,VANCOUVER V6T 1W5,BRITISH COLUMBI,CANADA
[2] DAVID DUNLAP OBSERV,RICHMOND HILL,ONTARIO,CANADA
[3] QUEENS UNIV,ASTRON GRP,KINGSTON,ONTARIO,CANADA
[4] UNIV BRITISH COLUMBIA,INST ASTRON,VANCOUVER,BRITISH COLUMBI,CANADA