SIMEONOV , P.S. and BAINOV, D.D. 1991. APPLICATION OF THE METHOD OF THE TWO-SIDED APPROXIMATIONS TO THE SOLUTION OF THE PERIODIC PROBLEM FOR IMPULSIVE DIFFERENTIAL EQUATIONS. Tamkang Journal of Mathematics. 22, 3 (Sep. 1991), 275–284. DOI:https://doi.org/10.5556/j.tkjm.22.1991.4612.