@article{MZ_1996__222_3_174899,
     author = {Mitsuru Sugimoto},
     title = {Estimates for hyperbolic equations with non-convex characteristics.},
     journal = {Mathematische Zeitschrift},
     pages = {521--532},
     publisher = {mathdoc},
     volume = {222},
     number = {3},
     year = {1996},
     zbl = {0867.35013},
     url = {http://geodesic.mathdoc.fr/item/MZ_1996__222_3_174899/}
}