Comparison of stable carbon isotope ratios in the whole wood, cellulose and lignin of oak tree - rings Dr. Ron Towner from the Laboratory of Tree - Ring Research at the University of Arizona explains the principles behind dendrochronology and why this dating (myintimcity.com)
The use of carbon isotope ratio (CIR) testing as a means of identifying the presence of exogenous (synthetic) testosterone in an athlete's body was developed in part under the direction of Don Catlin. (sbnation.com)
The event was confirmed by the American astronomer J.A. Eddy, using carbon isotope ratios in tree rings. (britannica.com)