Striated Solutions of Semilinear, Two-Speed Wave Equations Jeffrey RauchMichael Reed Indiana University Mathematics Journal 1985 text pdf 10.1512/iumj.1985.34.34020 10.1512/iumj.1985.34.34020 en Indiana Univ. Math. J. 34 (1985) 337 - 353 state-of-the-art mathematics http://iumj.org/access/