Wang, Jiantian; Jin, Shuze Null condition for quasi-linear wave equation in two space dimensions. (Chinese) Zbl 1160.35480 J. Nanjing Norm. Univ., Nat. Sci. Ed. 20, No. 4, 6-13 (1997). MSC: 35L70 Second-order nonlinear hyperbolic equations PDF BibTeX XML Cite \textit{J. Wang} and \textit{S. Jin}, J. Nanjing Norm. Univ., Nat. Sci. Ed. 20, No. 4, 6--13 (1997; Zbl 1160.35480)