1. BHP Minerals, P.O. Box 188, Wallsend, New South Wales 2287, Australia.
2. 11 Wildflower Street, Capalaba, Queensland 4157, Australia.
3. P.O. Box 4087, Mulgrave, Victoria 3170, Australia.
4. CSIRO Telecommunications and Industrial Physics, P.O. Box 218 Lindfield, New South Wales 2070, Australia.