Analytic Hypo-Ellipticity and Propagation of Regularity for a System of Microdifferential Equations with Non-Involutory Characteristics. Toshinori Oaku — 1984 Mathematische Annalen
A Canonical Form of a System of Microdifferential Equations with Non-Involutory Characteristics and Branching of Singularities. Toshinori Ôaku Inventiones mathematicae
Boundary value problem for Fuchsian partial differential equations and reflection of singularities Toshinori Ôaku — 1992 Banach Center Publications