Singh, S., Giri, M.K., Singh, M. and Giri, N.K. 2019. A clinical comparative study of intraperitoneal instillation of ropivacaine alone or ropivacaine with nalbuphine for postoperative analgesia in laparoscopic cholecystectomy. Anaesthesia, Pain & Intensive Care. (Jan. 2019), 335-339.