Prabu, R. K., P. Rani, and N. Madhu. “Comparison of Morphine and Fentanyl in Attenuation of Intra Operative Stress Response under General Anesthesia: A Randomized Double Blinded Study”. Asian Journal of Medical Sciences, vol. 5, no. 4, May 2014, pp. 65-68, doi:10.3126/ajms.v5i4.9796.