M. Sato (, ) introduced a new class of generalized functions, called hyperfunctions, as the n-th derived sheaf of the sheaf of holomorphic functions. He left without proof many details in these papers. To this day, subsequent papers of mathematicians, especially Japanese, completed these "gaps" (, , , , , , ). Hyperfunctions have many important properties which are indispensable for an exquisite theory of partial differential equations, microfunctions, micro-local analysis, Fourier transform (cf. ). They became a major tool of several areas of analysis and applications.