Hafiza Armish Siraj, Waqar Jeelani, and Maheen Ahmed. “Perception of Different Combinations of Tones of Lip Vermilion and Gingiva on Smile Attractiveness”. Pakistan Orthodontic Journal, vol. 14, no. 2, Dec. 2022, pp. 89-96, https://poj.org.pk/index.php/poj/article/view/332.