De La Corte, Flávio Desessards, et al. “Early Pregnancy Diagnosis in the Mare Using Ultrasound”. Brazilian Journal of Veterinary Research and Animal Science, vol. 31, no. 3-4, Dec. 1994, pp. 282-7, https://doi.org/10.11606/issn.1678-4456.bjvras.1994.52078.