Anisentropic One-Dimensional Unsteady Magnetogasdynamic Flow J. Helliwell Indiana University Mathematics Journal 1965 text pdf 10.1512/iumj.1965.14.14036 10.1512/iumj.1965.14.14036 en Indiana Univ. Math. J. 14 (1965) 523 - 540 state-of-the-art mathematics http://iumj.org/access/