Toral-Cruz, H., J. L. Vázquez-Ávila, R. Sánchez-Lara, J. A. Trejo-Sánchez, and J. Alvarez-Chavez. “A Survey on Quality of Service in the Voice Over IP Technology”. European Scientific Journal, ESJ, Vol. 14, no. 10, Sept. 2018, https://eujournal.org/index.php/esj/article/view/11218.