The method of mixed monotony and second order boundary value problems
We develop a technique which we call the method of mixed monotony that investigates the question whether it is possible to construct monotone sequences that converge to a solution of initial and periodic boundary value problems for first order differential systems even when the right- hand side function f does not possess any monotone properties. Of course, it is well known that if f satisfies certain mixed quasimonotone properties such construction is possible.
scientific article; zbMATH DE number 3975386