Journal of Applied Mathematics and Stochastic Analysis Volume 10 (1997), Issue 3, Pages 273-278doi:10.1155/S1048953397000348
Consider the problem {y′(t)=f(t,y(t),λ),t∈J=[0,b],y(0)=k0,G(y,λ)=0.. Employing the method of upper and lower solutions and the monotone iterative technique, existence of extremal solutions for the above equation are proved.