Mazzarello, Vittorio, et al. “Lip Plumper: Non Invasive in Vitro Study of Moisturizing and Volumizing Effect”. Italian Journal of Anatomy and Embryology, vol. 115, no. 1/2, Nov. 2010, p. 109, https://oajournals.fupress.net/index.php/ijae/article/view/4494.