The Singular Cauchy Problem for a Quasi-Linear Hyperbolic Equation of Second Order Hajimu Ogawa Indiana University Mathematics Journal 1963 text pdf 10.1512/iumj.1963.12.12058 10.1512/iumj.1963.12.12058 en Indiana Univ. Math. J. 12 (1963) 847 - 856 state-of-the-art mathematics http://iumj.org/access/