lecturing. Politically Hahn was a socialist and was chairman of the Association of Socialist University Teachers. Hahn's contributions to mathematics include the Hahn–Banach theorem and (independently of Banach and Steinhaus) the uniform boundedness principle. Other theorems include: the Hahn decomposition theorem; the Hahn embedding theorem; the Hahn–Kolmogorov theorem; the Hahn–Mazurkiewicz theorem; the Vitali–Hahn–Saks theorem. Hahn authored the book : according to Arthur Rosenthal, "... (it) formed a great advance in the Theory of Real functions and had a great influence on the further development of this theory". He was also a co-author of the book Set Functions, published in 1948 by Arthur Rosenthal, fourteen years after his death in Vienna in 1934. In 1921 he received the Richard Lieben Prize. In 1926 he was the president of the German Mathematical Society. In 1928 he was an Invited Speaker at the International Congress of Mathematicians in Bologna. Publications All his mathematical and philosophical works, except all books and all but one of his book reviews, are published in the three volumes , and of his "Collected papers". (freely available at the Internet Archive). . . See also Domain (mathematical analysis) Mathematical analysis Notes External links 1879 births 1934 deaths Austrian Jews Scientists from Vienna 20th-century Austrian mathematicians Vienna Circle Topologists Set theorists Austrian agnostics Austrian socialists Jewish agnostics Jewish scientists Austro-Hungarian mathematicians Academic staff of Chernivtsi University Functional analysts