The Growth and Decay of Sonic Discontinuities in Ideal Gases T. Thomas Indiana University Mathematics Journal 1957 text pdf 10.1512/iumj.1957.6.56022 10.1512/iumj.1957.6.56022 en Indiana Univ. Math. J. 6 (1957) 455 - 469 state-of-the-art mathematics http://iumj.org/access/