Trujillo-Ortega, M.E., et al. “A Study of Piglets Born by Spontaneous Parturition under Uncontrolled Conditions: Could This Be a Naturalistic Model for the Study of Intrapartum Asphyxia?”. Acta Biomedica Atenei Parmensis, vol. 78, no. 1, Apr. 2007, pp. 29-35, https://mattioli1885journals.com/index.php/actabiomedica/article/view/1924.