PageHeader : Funkcialaj Ekvacioj, 20 (1977) 77-95 Title : On the Equation $u_{tt}-u_{xx}=F(x, t, u, u_{x}, u_{t})$ AuthorInfo : By AuthorInfo : Yukiyoshi EBIHARA AuthorInfo : (Fukuoka University, Japan) section : 0. Introduction section : 1. Fundamental concept section : 2. The approximating solutions section : 3. Theorems section : References