P. P. V. V. B., V. C. R. Konda, and L. K., “A prospective, randomized, double blind, comparative study of intramuscular nalbuphine hydrochloride, butorphanol tartrate and pentazocine lactate for post-operative pain relief following abdominal hysterectomy”, Int J Basic Clin Pharmacol, vol. 5, no. 6, pp. 2326–2331, Dec. 2016.