Bainov, D. D., and M. B. Dimitrova. “Sufficient Conditions for Oscillation of Solutions of Nonlinear Impulsive Differential Equations With a Retarded Argument”. The Journal of the Indian Mathematical Society 66, no. 1-4 (December 1, 1999): 49–59. Accessed April 29, 2024. https://www.informaticsjournals.com/index.php/jims/article/view/21931.