“…In the case of constant p, the second-order regularity of the weak solutions to equations or systems of parabolic equations of the type (1.4) u t = ∆ p u + f, p > 1, were studied by many authors. We refer to [15] for the global estimates (1.3) and to [15,21,22,16,11,20,29,1] for local results, see also references therein. The works [21,22] deal with the homogeneous equation (1.4).…”