K. Somu, S. B. S., S. Hebbar, S. G., and M. V. Pai, “Sonographic assessment of fetal head deflexion using occiput: spine angle measured during first stage of labour and its role in predicting the mode of delivery among nulliparous women”, Int J Reprod Contracept Obstet Gynecol, vol. 8, no. 8, pp. 3025–3030, Jul. 2019.