N. Gupta, S. Gupta, A. Agarwal, S. Agarwal, and R. Mahto, “A comparison of visual analog scale and Wong Baker facial pain scale for pain measurement in post lower caesarean section case”, Int J Reprod Contracept Obstet Gynecol, vol. 5, no. 9, pp. 3032–3035, Feb. 2017.