M, APARNA., et al. “Nasolabial Angle in Patients With Maxillary Incisor Proclination- A Retrospective Study”. The Journal of Contemporary Issues in Business and Government, vol. 27, no. 2, Apr. 2021, pp. 427-33, http://www.cibgp.com/index.php/1323-6903/article/view/945.