Gupta, P., S. Kumar, and A. K. Keshari. “Assessment of Preoperative Factors for Challenging Laparoscopic Cholecystectomy”. International Journal of Health and Clinical Research, vol. 4, no. 8, Apr. 2021, pp. 189-91, https://ijhcr.com/index.php/ijhcr/article/view/1444.