Sforza, C., and V. F. Ferrario. “Three-Dimensional Analysis of Facial Morphology: Growth, Development and Aging of the Orolabial Region”. Italian Journal of Anatomy and Embryology, vol. 115, no. 1/2, Sept. 2010, pp. 141-5, https://oajournals.fupress.net/index.php/ijae/article/view/1072.