Madureira, Ed Hoffmann, et al. “Progesterone Concentrations Measured by Radioimmunoassay in Blood Plasma and in Fat-Free Milk of Gir Breed Cows IBos indicus). Determinations During Oestrus Cycle. Early Pregnancy Diagnosis”. Brazilian Journal of Veterinary Research and Animal Science, vol. 27, no. 2, Dec. 1990, pp. 247-53, https://doi.org/10.11606/issn.0000-0000.272247-253.