HOSSEINI, V. S.; YEKTA, R.; MARASHI, S.; MARASHI, S. M. The Efficacy of Melatonin, Clonidine and Gabapentin in Reducing Preoperative Anxiety and Postoperative Pain in Patients Undergoing Laparoscopic Cholecystectomy: A Randomized Clinical Trial. Archives of Anesthesiology and Critical Care, v. 1, n. 4, p. 120-125, 23 nov. 2015.