[5][6] This usage differs from the recommendation by van der Plicht & Hogg,[7] followed by the Quaternary Science Reviews,[8][9] both of which requested that publications should use the unit "a" (for "annum", Latin for "year") and reserve the term "BP" for radiocarbon estimations.
[14][15] Beginning in 1954, metrologists established 1950 as the origin year for the BP scale for use with radiocarbon dating, using a 1950-based reference sample of oxalic acid.
According to scientist A. Currie Lloyd: The problem was tackled by the international radiocarbon community in the late 1950s, in cooperation with the U.S. National Bureau of Standards.
A large quantity of contemporary oxalic acid dihydrate was prepared as NBS Standard Reference Material (SRM) 4990B.
[citation needed] It also marked[3] the publication of the first radiocarbon dates in December 1949,[17] and 1950 also antedates large-scale atmospheric testing of nuclear weapons, which altered the global ratio of carbon-14 to carbon-12.