Chaudhari, V. L., A. B. Thakare, and Y. N. Zanwar. “Epidural Butorphanol : Comparison of Two Different Doses in Lower Abdominal Surgery”. International Journal of Health and Clinical Research, vol. 3, no. 10, Nov. 2020, pp. 182-6, https://ijhcr.com/index.php/ijhcr/article/view/337.