“…By a similar reasoning to the used in the Proposition 4.3, it can be proved that we can apply Lemma I.1 in [8] to show that the pair (u, u) := (εΨ, Ke) is a sub-supersolution of (1.4), provided that ε and K are sufficiently small and large, respectively. Now, the strong maximum principle shows (4.8), see Lemma 2.1 in [7]. This completes the proof.…”