“…Moreover, Lemma 5 applies, because passivity is given (Lemma 6), and the uniquely defined solution x satisfies the estimates (5.2)-(5.4), and thus, it satisfies the estimate (5.10). Hence, the coupled system (5.11)-(5.14) defines a map from M to itself, The proof from [2] applies also to our index-2 case. Hence, by Schauder's fixed point theorem, T admits a fixed point (x, Φ, φ), which solves the original problem (4.1)-(4.4).…”