BAINOV, D. D., S. I. KOSTADINOV, N. V. MINH, and P. P. ZABREIKO. “A TOPOLOGICAL CLASSIFICATION OF DIFFERENTIAL EQUATIONS WITH IMPULSE EFFECT”. Tamkang Journal of Mathematics, vol. 25, no. 1, Mar. 1994, pp. 15-27, doi:10.5556/j.tkjm.25.1994.4420.