Simonetti, L., Gardón, J.C. and Ramos, G. (1999) “Residual levels on medroxyprogesterone acetate (MAP) impregnated sponges after estrus synchronization treatment in cyclic ewes”, Brazilian Journal of Veterinary Research and Animal Science, 36(5), pp. 240–243. doi:10.1590/S1413-95961999000500003.