Monotone iterative technique for a class of four point BVPs with reversed ordered upper and lower solutions

Consider the class of four point nonlinear BVPs −w″(x) = f(x,w,w′),x ∈ I, w′(0) = 0,w(1) = δ 1w(η1) + δ2w(η2), where f ∈ (I × ℝ × ℝ, ℝ) is continuous, I = [0, 1], η1,η2 ∈ (0, 1) such that η1 ≤ η2 a...