1. Bainov, D., Kamont, Z., Minchev, E.: On the impulsive partial differential-functional inequalities of first order. Utilitas Mat. (to appear).
2. Bainov, D., Lakshmikantham, V., Simeonov, P.: Theory of impulsive differential equations. Singapore: World Scientific, 1989.
3. Bainov, D., Simeonov, P.: Systems with impulse effect, stability theory and applications. Chichester: Ellis Horwood, 1989.
4. Bassanini, P., Galaverni, M.: Contrazioni multiple, sistemi iperbolici, é problema del laser. Atti Sem. Mat. Fis. Univ. Modena31, 1–19 (1982).
5. Brandi, P., Kamont, Z., Salvadori, A.: Approximate solutions of mixed problems for first order partial differential-functional equations. Atti Sem. Mat. Fis. Univ. Modena39, 277–302 (1991).