Mario Cappellette Jr, et al. “In Vitro Comparison of Friction Generated by Various Models of Self-Ligating and Conventional Brackets While Performing Retraction With Sliding Mechanics”. Global Journal of Medical Research, vol. 17, no. J2, July 2017, pp. 13-25, https://medicalresearchjournal.org/index.php/GJMR/article/view/1392.