“…Due to this loss of regularity, it is necessary to work with weak solutions; moreover, to single out a physically relevant and unique weak solution, we need to impose additional "entropy inequalities", in the spirit of Kruzhkov [63]. Early results on hyperbolic-parabolic equations were obtained by Volpert, Hudjaev [78]; see also [80,82,81], [74], [28], [19] and references cited therein, and [76], [37], [32]. L 1 entropy techniques for degenerate convection-diffusion equations like (3), which take into account both hyperbolic and parabolic features, were developed by Carrillo [29] for the homogeneous Dirichlet problem in bounded domains.…”