Iqbal, Abdullah, et al. “PREOPERATIVE ASSESSMENT OF SCORING SYSTEM DESIGNED FOR PREDICTION OF DIFFICULT CHOLECYSTECTOMY IN PATIENTS WITH SYMPTOMATIC GALL STONES”. Pakistan Armed Forces Medical Journal, vol. 70, no. 2, Apr. 2020, pp. 610-16, https://pafmj.org/PAFMJ/article/view/4242.