Allen R M, Redshaw M R, Holdsworth R
J Reprod Fertil. 1980 Jan;58(1):89-93. doi: 10.1530/jrf.0.0580089.
Progesterone levels in the milk of cows were determined by two radioimmunoassay methods. Excellent correlation (r = 0.95) was found between the method using an iodinated radioligand and that using a conventional tritiated tracer.