On the Singularities of the Solution to the Cauchy Problem with Singular Data in the Complex Domain. Takao Kobayashi — 1984 Mathematische Annalen
Propagation of singularities for a first order semi-linear system in ℂ n + 1 Takao Kobayashi — 1985 Annali della Scuola Normale Superiore di Pisa - Classe di Scienze