Tunç, C., and S. A. Mohammed. “New Results on Exponential Stability of Nonlinear Volterra Integro-Differential Equations With Constant Time-Lag.”. Proyecciones (Antofagasta, On Line), vol. 36, no. 4, 1, pp. 615-39, https://www.revistaproyecciones.cl/index.php/proyecciones/article/view/2539.