Eduard Helly
died 74 years ago
28th November 1943

Eduard Helly worked on functional analysis and proved the Hahn-Banach theorem in 1912 fifteen years before Hahn published essentially the same proof and 20 years before Banach gave his new setting.

Find out more at:
http://www-history.mcs.st-andrews.ac.uk/Mathematicians/Helly.html