“…[28]. Although many interesting systems of the form (1) arise as dispersionless limits of multidimensional soliton equations [39] or within the R-matrix approach [3] and, therefore, should be regarded as integrable, no intrinsic definition of the integrability for multidimensional quasilinear systems has been proposed until recently. In particular, the standard symmetry approach [32,33], which proves to be extremely effective in the case of higher order evolution equations and systems, does not seem to work in this context.…”