1. Wadsworth Center for Laboratories and Research, New York State Department of Health, Albany, NY 12201.
2. Department of Archeology, Simon Fraser University, Burnaby, British Columbia, Canada V5A 1S6, and Tandem Accelerator Laboratory, McMaster University, Hamilton, Ontario, Canada L8S 4K1.
3. Lamont Doherty Geological Observatory, Columbia University, Palisades, NY 10964.