J. A. Valencia-Álvarez, Y. Montoya-Góez, A. Peláez-Vargas, P. M. Jaramillo-Vallejo, and C. García-García, “Friction evaluation in stainless steel arches with and without glass coating using the Sol-Gel method”, Rev Fac Odontol Univ Antioq, vol. 20, no. 2, pp. 161–170, Aug. 2009.