Nonlinear delay integral inequalities for piecewise continuous functions and applications. Hristova, S.G. — 2004 JIPAM. Journal of Inequalities in Pure & Applied Mathematics [electronic only]
Method of the quasilinearization for nonlinear impulsive differential equations with linear boundary conditions. Eloe, P.; Hristova, S.G. — 2002 Electronic Journal of Qualitative Theory of Differential Equations [electronic only]
Quasilinearization for the periodic boundary value problem for systems of impulsive differential equations. Hristova, S.G.; Vatsala, A.S. — 2006 Journal of Applied Mathematics and Stochastic Analysis
Monotone-iterative technique of Lakshmikantham for the initial value problem for a differential equation with a step function. Hristova, S.G.; Rangelova, M.A. — 2002 International Journal of Mathematics and Mathematical Sciences