After two decades a second anchor for the VPDB delta13C scale.

Tyler B. Coplen*, Willi A. Brand, Matthias Gehre, Manfred Gröning, Harro A. J. Meijer, Blaza Toman and R. Michael Verkouteren US Geological Survey, 431 National Center, Reston, VA 20192, USA Max-Planck-Institute for Biogeochemistry, Beutenberg Campus, P.O. Box 100164, 07701 Jena, Germany UFZ Umweltforschungszentrum Leipzig-Halle GmbH, Labor für Stabile Isotope, Permoserstrasse 15, 04318 Leipzig, Germany International Atomic Energy Agency, Isotope Hydrology Laboratory, P.O. Box 100, A-1400 Vienna, Austria Centrum voor Isotopen Onderzoek (CIO), Rijksuniversiteit Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands National Institute of Standards and Technology, Information Technology Laboratory, Mail Stop 8980, Gaithersburg, MD 20899, USA National Institute of Standards and Technology, Chemical Science and Technology Laboratory, Mail Stop 8371, Gaithersburg, MD 20899, USA