C. H. C. Viana, R. P. de Arruda, A. S. Moretti, and J. A. Visintin, “Ovarian cysts, rectal palpation and ultra-rectal ultra- sonography diagnosis in sows: literature review and two clinical report studies”, Braz. J. Vet. Res. Anim. Sci., vol. 35, no. 2, pp. 64–68, Jan. 1998, doi: 10.1590/S1413-95961998000200003.