Geodesic
The main series of nonhomogeneous systems of hydrodynamic type with constant matrices possessing $1^{st}$ order conservation laws
Fundamentalʹnaâ i prikladnaâ matematika, Tome 1 (1995) no. 3, pp. 641-648 
E. I. Ganzha. The main series of nonhomogeneous systems of hydrodynamic type with constant matrices possessing $1^{st}$ order conservation laws. Fundamentalʹnaâ i prikladnaâ matematika, Tome 1 (1995) no. 3, pp. 641-648. http://geodesic.mathdoc.fr/item/FPM_1995_1_3_a4/
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     title = {The main series of nonhomogeneous systems of hydrodynamic type with constant matrices possessing $1^{st}$ order conservation laws},
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Voir la notice de l'article provenant de la source Math-Net.Ru

Let $u_t^i=v_iu_x^i+f_i(u)$, $i=1,\ldots,n$ be a system of PDE with constant $v_i$. We give a classification of such systems possessing nontrivial conservation laws $dg(u,u_x)/dt=dh(u,u_x)/dx$ and their explicit form for two main series. The third (and the last) main series is shown to be nontrivial. Some examples of such systems are new.

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