PageHeader : Funkcialaj Ekvacioj, 45 (2002) 209-222 Title : Forced Vibrations of Absffact Wave Equations AuthorInfo : By AuthorInfo : Michal $\mathrm{F}\mathrm{E}\check{\mathrm{C}}\mathrm{K}\mathrm{A}\mathrm{N}$ AuthorInfo : (Comenius University, Slovakia) section : 1. Introduction section : 2. Nonresonant cases section : A weak T-periodic solution of (1.5) is some u $\in L^{2}(S^{T}, $ Y) satisfying section : Theorem 2.3. Assume section : 3. Resonant cases section : 4. Some remarks on the condition (1.4) section : References