A Note on Shocks in Nonlinear Similarity Fields Nima GeffenLevi Lustman Indiana University Mathematics Journal 1976 text pdf 10.1512/iumj.1976.25.25033 10.1512/iumj.1976.25.25033 en Indiana Univ. Math. J. 25 (1976) 397 - 402 state-of-the-art mathematics http://iumj.org/access/