M. Dreher, M. Reissig, International Society for Analysis, Applications and Computation, 2, Partial Differential and Integral Equations, 1999, 303
Tatsuo Nishitani, “Hyperbolicity of two by two systems with two independent variables”, Communications in Partial Differential Equations, 23:5-6 (1998), 1061
G. R. Oganesyan, E. A. Taroyan, “Ustoichivost zadachi Koshi dlya slabo giperbolicheskikh uravnenii chetvertogo poryadka”, Uch. zapiski EGU, ser. Fizika i Matematika, 1997, no. 1, 89–93
Enrico BERNARDI, Antonio BOVE, “Geometric transition for a class of hyperbolic operators with double characteristics”, Jpn. j. math, 23:1 (1997), 1
Enrico Bernardi, Antonio Bove, Partial Differential Operators and Mathematical Physics, 1995, 21
Enrico Bernardi, Antonio Bove, “Geometric transition for a class of hyperbolic operators with double characteristics”, Proc. Japan Acad. Ser. A Math. Sci., 71:4 (1995)
V. Ya. Ivrii, Encyclopaedia of Mathematical Sciences, 33, Partial Differential Equations IV, 1993, 149
Enrico Bernardi, Antonio Bove, Tatsuo Nishitani, “Levi conditions for hyperbolic operators with a stratified multiple variety”, Proc. Japan Acad. Ser. A Math. Sci., 68:3 (1992)
Tatsuo Nishitani, Lecture Notes in Mathematics, 1505, The Hyperbolic Cauchy Problem, 1991, 71
E. Bernardi, A. Bove, “Necessary and sufficient conditions for the well-posedness of the Cauchy problem for a class of hyperbolic operators with triple characteristics”, J Anal Math, 54:1 (1990), 21
E. Bernardi, A. Bove, “Propagation of Gevrey singularities for a class of operators with triple characteristics, I”, Duke Math. J., 60:1 (1990)
E. Bernardi, A. Bove, “Propagation of Gevrey singularities for a class of operators with triple characteristics, II”, Duke Math. J., 60:1 (1990)
Katsuju IGARI, “The characteristic Cauchy problem at a point where the multiplicity varies”, Jpn. j. math, 16:1 (1990), 119
Enrico Jannelli, “On the Symmetrization of the Principal Symbol of Hyperbolic Equations”, Communications in Partial Differential Equations, 14:12 (1989), 1617
Enrico Bernardi, Antonio Bove, “Geometric results for a class of hyperbolic operators with double characteristics”, Communications in Partial Differential Equations, 13:1 (1988), 61
E. Bernardi, A. Bove, C. Parenti, Lecture Notes in Mathematics, 1340, Calculus of Variations and Partial Differential Equations, 1988, 23
Enrico Bernardi, Antonio Bove, “The Cauchy problem for a class of hyperbolic operators with triple characteristics”, Proc. Japan Acad. Ser. A Math. Sci., 64:10 (1988)
Tatsuo Nishitani, “Système involutif d'opérateurs effectivement hyperboliques”, Proc. Japan Acad. Ser. A Math. Sci., 63:4 (1987)
V. V. Kucherenko, L. Yu. Motylev, “The limits of applicability of the canonical operator method for nonstrictly hyperbolic equations with nonsmooth characteristics”, Math. USSR-Izv., 29:1 (1987), 95–117
Tatsuo NISHITANI, Hyperbolic Equations and Related Topics, 1986, 235