1. Nonlinear Semigroups and Differential Equations in Banach Spaces;Barbu,1976
2. The solution by iteration of nonlinear functional equations in Banach spaces;Browder;Bull. Amer. Math. Soc.,1966
3. Equations d’évolution non linéaires: solutions bornées et périodiques;Haraux;Ann. Inst. Fourier, Grenoble,1978
4. An existence result for a nonlinear hyperbolic system;Luca;Diff. Integral Equations,1995
5. R. Luca, Probleme la limită pentru sisteme cu derivate parţiale de tip hiperbolic şi aplicaţii, Doctoral Thesis, Department of Mathematics, “Al. I. Cuza” University of Iaşi, 1995.