Kravchenko, Borys, et al. “A Comparative Analysis of Single-Port and Four-Port Laparoscopic Cholecystectomies in Patients With Chronic Calculous Cholecystitis”. Journal of Education, Health and Sport, vol. 9, no. 6, June 2019, pp. 514-21, https://apcz.umk.pl/JEHS/article/view/7151.