Kajitani, K. and Yuzawa, Y. 2009. The Cauchy problem for hyperbolic systems with Hölder continuous coefficients with respect to the time variable. ANNALI SCUOLA NORMALE SUPERIORE - CLASSE DI SCIENZE. 5, 4 (Dec. 2009), 465-482. DOI:https://doi.org/10.2422/2036-2145.2006.4.03.