“…(1), G 1 (t, y(t)) and G 2 (t, y(t)) are given continuous functions which are nonlinear with respect to y(t) and t. These types of equations arises in a variety of applications in many fields including continuum mechanics, potential theory, geophysics, electricity and magnetism, antenna synthesis problem, communication theory, mathematical economics, population genetics, radiation, the particle transport problems of astrophysics and reactor theory, fluid mechanics, etc ( see e.g. [1,3,10,11,15,21,22,24]). …”