Opérateurs différentiels partiellement hypoelliptiques Y. Kato — 1966 Bulletin de la Société Mathématique de France
Green functions and spectra on free products of cyclic groups K. Aomoto; Y. Kato — 1988 Annales de l'institut Fourier Green functions of a stochastic operator on a free product of cyclic groups are explicitly evaluated as algebraic functions. The spectra are investigated by Morse theoretic argument.