1. Lamont-Doherty Earth Observatory of Columbia University, 61 Route 9W/Post Office Box 1000, Palisades, NY 10964, USA.
2. AMS 14C lab, ETH Hoenggerberg HPK H27 and H30, CH-8093 Zurich, Switzerland.
3. University of Southern California, 3651 Trousdale Parkway, Los Angeles, CA 90089, USA.