“…Consider two shock curves of first family, which start from the points (r 0 , s 1 ) = (r(U 0 ), s(U 1 )) and (r 0 , s 0 ) = (r(U 0 ), s(U 0 )) and are continuous to the points (r, s 2 ) and (r, s), respectively. Then there exists a constant c 0 > 0 such that, for c ≥ c 0 , Again, following [1] (see also [24]), we obtain the wave interaction estimates corresponding to Lemma 3.4 and conclude the existence of a global entropy solution U µ to (4.1) by the front-tracking method.…”