Jean Leray（1906—1998）
Jean Leray was first and foremost an analyst. His involvement with algebraic topology was initially incidental and became later, at first for nonmathematical reasons, a topic of major interest for him for about ten years. His papers are written with his own notation and conventions, which, for the most part, have not been adopted and are consequently little read today. But it is there that sheaves and spectral sequences originated and were first used, so this work has exerted an immense influence on the further course of algebraic topology and of the emerging homological algebra. It divides naturally into three parts.