H. Fan, ONE-PHASE RIEMANN PROBLEM AND WAVE INTERACTIONS IN SYSTEMS OF CONSERVATION-LAWS OF MIXED-TYPE, SIAM journal on mathematical analysis, 24(4), 1993, pp. 840-865
The Riemann problem for any Riemann data lying outside of the elliptic
region of a system of conservation laws of mixed type is established.
The approach is a vanishing viscosity one. The solutions constructed
are also admissible by the traveling wave criterion. The structure of
the solutions is analyzed. Interactions among phase boundaries and sho
cks are studied.