Ernst Leonard Lindelöf (1870-3-7 à 1946-6-3) was born in Helsinki, Finland. Professor of mathematics in University of Helsinki 1903-1938. Lindelöf was the founder of the internationally noted Finnish school of function theory. Rolf Nevanlinna and Lars Ahlfors were his pupils. Most studies of Lindelöf were on the complex analysis, theory of differential equations (e.g. Picard-Lindelöf theorem) and topology (see e.g. Lindelöf space). One of them, “Mémoire sur la théorie des fonctions entières de genre fini” (1902) complements substantially the theory of entire functions; also “Mémoire sur certaines inégalités dans la théorie des fonctions monogènes (1908), containing a new simple proof of Picard's theorem, was important. Lindelöf has made excellent textbooks of mathematics: “Le calcul des résidus et ses applications à la théorie des fonctions” (1905), “Johdatus korkeampaan analyysiin” (`Introduction to the higher analysis'; 1912), “Differentiali- ja integralilasku ja sen sovellutukset I-IV” (`Differential and integral calculus with applications I-IV'; 1928-1946).