Center for Isotope Geochemistry, Lawrence Berkeley National Lab, Berkeley, CA 94720 United States ; Department of Plant Biology, Cornell University, Ithaca, NY 14853 United States
Center for AMS, UC/LLNL L-397, Livermore, CA 94551 United States
Marine Biological Laboratories, 7 MBL Road, Woods Hole, MA 02543 United States
Lamont-Doherty Earth Obs., Rte. 9-W, Palisades, NY 10964 United States