“…Since generally no maximum principle holds for parabolic systems, the proof of L ∞ bounds is a challenging problem [20], and ad hoc techniques must be employed to deduce the existence of solutions of particular problems. A useful methodology avoiding the L ∞ bounds requirement of Amman's results was introduced in [10] and later generalized in a series of papers, see [7,8,11,9,12,20] and the references therein. However, this technique relies on the introduction of a Lyapunov functional needing of a particular crossdiffusion structure which is not satisfied by system (3) The nonlinear instability of these type of strongly coupled systems, as induced only by cross diffusion terms, has been also an active area of research, see [15,26,6,16] and the references therein.…”