Ni, Xiu, Xiang Zhao, Mengzhu Li, Quan Li, and Zhiqiang Liu. “Thoracic Epidural Anesthesia for Gas-Free Trans-Umbilical Single Port Laparoscopic Cholecystectomy: A Case Report”. International Surgery Journal 4, no. 1 (December 13, 2016): 420–422. Accessed November 10, 2025. https://www.ijsurgery.com/index.php/isj/article/view/746.