Khan, W. U., S. Abdullah, I. khan, and H. U. Jan. “Effect of Non-Extraction Orthodontic Treatment of Impacted and Malposed Maxillary Canines on Upper Lip Strain and Thickness”. Pakistan Orthodontic Journal, vol. 7, no. 1, Oct. 2015, pp. 25-29, https://www.poj.org.pk/index.php/poj/article/view/111.