Mumtaz, M., Shaheed, M., Zia, A. U. and Illyas, K. (2020) “Comparison of mean upper lip length in individuals with competent lips, lips apart and incompetent lips”, Pakistan Orthodontic Journal, 12(1), pp. 61–64. Available at: https://www.poj.org.pk/index.php/poj/article/view/287 (Accessed: 11 September 2025).