[1] Radboud Univ Nijmegen, IMAPP, Dept Astrophys, POB 9010, NL-6500 GL Nijmegen, Netherlands
[2] Curtin Univ, Int Ctr Radio Astron Res, GPO Box U1987, Perth, WA 6845, Australia
[3] Natl Res Council Canada, Domin Radio Astrophys Observ, Herzberg Astron & Astrophys, POB 248, Penticton, BC V2A 6J9, Canada
[4] Univ Alberta, Dept Phys, CCIS 4-183, Edmonton, AB T6G 2E1, Canada
[5] Univ Southampton, Sch Phys & Astron, Southampton SO17 1BJ, Hants, England
[6] Univ Cape Town, Dept Astron, Private Bag X3, ZA-7701 Rondebosch, South Africa
[7] Amer Assoc Variable Star Observers, 49 Bay State Rd, Cambridge, MA 02138 USA