[1] QUEENS UNIV BELFAST,DEPT PURE & APPL PHYS,BELFAST BT7 1NN,ANTRIM,NORTH IRELAND
[2] QUEENS UNIV BELFAST,DEPT APPL MATH & THEORET PHYS,BELFAST BT7 1NN,ANTRIM,NORTH IRELAND
[3] OHIO STATE UNIV,DEPT ASTRON,COLUMBUS,OH 43210
[4] ARMAGH OBSERV,ARMAGH BT61 9DG,NORTH IRELAND
[5] DARESBURY LAB,WARRINGTON WA4 4AD,CHESHIRE,ENGLAND