Uniqueness of solutions for some nonlinear Dirichlet problems

We consider here a class of nonlinear Dirichlet problems, in a bounded domain Omega of the form { -div(a(x, u)delu) + div(Phi(u)) = f in Omega, u = 0 on thetaOmega, investigating the problem of uniqueness of solutions. The functions Phi(s) and s --> a(x, s) satisfy rather general assumptions of locally Lipschitz continuity (with possibly exponential growth) and the datum f is in L-1(Omega). Uniqueness of solutions is proved both for coercive a(x, s) and for the case of a(x, s) degenerating for s large