“…where ∆ s denotes the s-Laplacian operator ∆ s u := ∇ • (|∇u| s−2 ∇u) for s ∈ (1, ∞). Differential equations of type (2) have attracted a great deal of attention in recent years, see, e. g., [4,8,31,32,30,5,6,13,18,3] for scalar equations, and [17,7] for systems. When p = q, equation (2) becomes −∆ p u = g(x, u), which has been studied extensively in the literature.…”