Hakan Çam, et al. “Study of Ideal Topical Pharyngeal Anesthesia in Upper Gastrointestinal System Endoscopy: A Double-Blind, Randomized, Controlled Trial”. Turkish Journal of Gastroenterology, vol. 27, no. 2, July 2019, pp. 103-7, https://tjg.avesjournals.com/index.php/tjg/article/view/3231.