[1] D. D. Bainov G. Kulev I. M. Stamova: Global Stability of the Solutions of Impulsive Differential-Difference Equations. SUT Journal of Mathematics, 31:55- 71, 1995. MR 1342766

[2] D. D. Bainov I. M. Stamova: On the Practical Stability of the Solutions of Impulsive Differential-Difference Equations with Variable Impulsive Perturbations. Journal of Mathemat. Analysis and Appl. 200:272-288, 1996. MR 1391149

[3] D. D. Bainov I. M. Stamova: Global Stability of the Solutions of Impulsive Differential-Difference Equations with Variable Impulsive Perturbations, COMPEL. The Int.Journal for Computation and Math, in Electrical and Electronic Engineering, 1:3-16, 1997.

[4] D. D. Bainov I. M. Stamova: Application of Lyapunov's Direct Method to the Investigation of the Stability of the Solutions of Impulsive Differential-Difference Equations with Variable Impulsive Perturbations. Applicable Analysis, 63:253- 269, 1996. MR 1624036

[5] G. K. Kulev D. D. Bainov: Global Stability of Sets for Systems with Impulses. Applied Mathematics and Computation, 29:255-270, 1989. MR 0977821

[6] V. Lakshmikantham D. D. Bainov, and P. S. Simeonov: Theory of Impulsive Differential Equations. World Scientific, Singapore, 1989. MR 1082551

[7] V. Lakshmikantham S. Leela, A. A. Martynyuk: Stability Analysis of Nonlinear Systems. Marcel Dekker Inc., New York, 1989. MR 0984861