Popko, I. Y., and D. V. Dmytriiev. “Changes of Immunological Reactivity During Surgery and in Postoperative Period Depending on Analgesic Regimen”. Pain Medicine, vol. 2, no. 1, Mar. 2017, pp. 28-33, https://painmedicine.org.ua/index.php/pnmdcn/article/view/43.