“…where p, q are real exponents, a, b are sufficiently smooth functions and Γ ∈ C 2 (R, R) (see [9,20,52,53,60,61] and the references therein for gradient estimates and related results in this direction). Another class of equations that have been extensively studied and whose nonlinearity is in the form of superposition of power-like nonlinearities are the Yamabe equations (see, e.g., [6,13,24,30]).…”