“Efficacy of Magnesium Sulphate As a Coadyuvant in Postoperative Analgesia in Patients Undergoing Open Cholecystectomy”. Boletin Médico de Postgrado, vol. 35, no. 2, Mar. 2020, pp. 7-13, https://revistas2.uclave.org/index.php/bmp/article/view/2571.