percent modern carbon
normalized and standardized value for the amount of the 14C isotope in a sample, calculated relative to the standardized and normalized 14C isotope amount of oxalic acid standard reference material, NIST SRM 4990b or NIST SRM 4990c or Sucrose (NIST SRM 8542) NIST SRM 4990b or NIST SRM 4990c or Sucrose (NIST SRM 8542) is the trade name of a product supplied by the US National Institute of Standards and Technology. This information is given for the convenience of users of this document and does not constitute an endorsement by ISO of the product named. Equivalent products can be used if they can be shown to lead to the same results.