「The regularity of solutions of the initial boundary value problem for quasi-linear symmetric hyperbolic systems with characteristic boundary」. Proceedings of the Conference on Nonlinear Evolution Bquations and Infinite-Dimensional Systems, World Scientific, Singapore. 1997. 165-172
The initial boundary value problem for symmetric hyperbolic systems with characteristic boundary
Qualitative Aspects and Applications of Nonlinear Evolution Equations (World Scientific) 1995