1. Modulus of continuity of the coefficients and loss of derivatives in the strictly hyperbolic Cauchy problem;Cicognani;J. Differ. Equ.,2006
2. Sur les équations hyperboliques avec des coefficients qui ne dépendent que du temps;Colombini;Ann. Sc. Norm. Super. Pisa, Cl. Sci. (4),1979
3. The well-posedness issue in Sobolev spaces for hyperbolic systems with Zygmund-type coefficients;Colombini;Commun. Partial Differ. Equ.,2015
4. Well-posedness of the Cauchy problem for a hyperbolic equation with non-Lipschitz coefficients;Colombini;Ann. Sc. Norm. Super. Pisa, Cl. Sci. (5),2002
5. On the optimal regularity of coefficients in hyperbolic Cauchy problems;Colombini;Bull. Sci. Math.,2003