A. Heibig et A. Sahel, A METHOD OF CHARACTERISTICS FOR SOME SYSTEMS OF CONSERVATION-LAWS, Comptes rendus de l'Academie des sciences. Serie 1, Mathematique, 322(1), 1996, pp. 37-42
We generalize the method of characteristics to some systems of conserv
ation laws. An entropy estimate, analogous to the Oleinik (E) inequali
ty in the scalar case, is established.