1. K. Kasahara—M. Yamaguti,Strongly hyperbolic systems of linear partial equations with constant coefficients, Mem. Coll. Sc. Univ. KYOTO33 (Ser (A), (1960), pp. 1–33.
2. Y. Oshime,Canonical forms of 3$3 strongly hyperbolic systems with real constant coefficients, J. Math. KYOTO Univ.,31 (1991), pp. 937–982.
3. G. Strang,On strong hyperbolicity, J. Math. KYOTO Univ.,6 (1967), pp. 397–417.
4. J. Vaillant,Systèmes fortement hyperboliques et systèmes symétriques, C.R.A.S. Acad. Sci. Paris, t.328—Série I (1999), pp. 407–412.
5. J. Vaillant,Systèmes fortement hyperboliques, dimension réduite et symétrie [à paraître].