1. S. Castillo, M. Pinto, Asymptotic formulae for solutions of delay-difference systems, in, Proceedings of the Second International Conference on Difference Equations and Applications, Veszprem, Hungary, 1995
2. S. Castillo, M. Pinto, Asymptotic integration of impulsive differential systems, nonelliptic case, Nonlinear Anal.
3. The Asymptotic Solution of Linear Differential Systems;Eastham,1989
4. A unified theory of asymptotic integration;Harris;J. Math. Anal. Appl.,1977
5. Asymptotic integration of linear differential equations;Hartman;Amer. J. Math.,1955