http://www.loc.gov/mods/v3 http://www.loc.gov/standards/mods/v3/mods-3-2.xsd
Algebraic and graphic methods for evaluating discordant lead-isotope ages
"Algebraic and graphic procedures for the calculation of a concordant age from discordant Pb²⁰⁶/U²³⁸, Pb²⁰⁷/U²³⁵, and Pb²⁰⁷/Pb²⁰⁶ age data using one to three samples."
by L.R. Stieff, T.W. Stern, and R.N. Eicher.
Shorter contributions to general geology
Professional paper (Geological Survey (U.S.)) ; 414-E