1. American Geophysical Union, 2000 Florida Ave. NW, Washington DC 20009-1277, USA
2. Cornell University, Ithaca NY 14853-0001, USA
3. Australian National University, Canberra, Australian Capital Territory 0200, Australia
4. Knowledge Motifs, San Mateo, CA 94401, USA
5. The Cambridge Crystallographic Data Centre, Cambridge, Cambridgeshire CB2 1EZ, UK