1. Monheit GD, Davis B. Nasolabial folds. In: Carru-thers J, Carruthers A, editors. Soft Tissue Augmentation. 2nd ed. Vol 99. Philadelphia, PA: Elsevier; 2008. p. 105-126.
2. Rizzatti-Barbosa CM, Meloto CB, Gomes SGE, Custodio W. Dental practice implications of systemic diseases affecting the elderly: a literature review. Braz J Oral Sci. 2008;1691-1699.
3. American Society of Plastic Surgeons [Internet]. 2012 plastic surgery procedural statistics. [Cited 2014 Jul 20]. Available from: http://www.plasticsurgery.org/news/plastic-surgery-statistics/2012-plastic-surgery-statistics.html.
4. Fagien S. Facial soft-tissue augmentation with injectable autologous and allogenic human tissue collagen matrix (autologen and dermalogen). Plast Reconstr Surg. 2000:105:362-73.
5. Romagnoli M, Belmontesi M. Hyaluronic acid-based fillers: theory and practice. Clin Dermatol. 2008;26(2):123-59.