. . "Hellmuth Kneser (16 April 1898 \u2013 23 August 1973) was a Baltic German mathematician, who made notable contributions to group theory and topology. His most famous result may be his theorem on the existence of a prime decomposition for 3-manifolds. His proof originated the concept of normal surface, a fundamental cornerstone of the theory of 3-manifolds.He was born in Dorpat, Russian Empire (now Tartu, Estonia) and died in T\u00FCbingen, Germany."@en . . "German mathematician" . "1973Z"^^ . . . "1973-08-23Z"^^ . . "1898Z"^^ . "Kneser, Hellmuth"@en . "1898-04-16Z"^^ . "Hellmuth Kneser"@en . .