PERSON@1 -LRB- NUMBER@1 April NUMBER@2 NUMBER@3 June NUMBER@4 -RRB- was a MISC@1 mathematician , known for his work in group theory , function theory , MISC@2 geometry , and on the connections between geometry and group theory .

He became known for his work in group theory , function theory , MISC@2 geometry , and on the connections between geometry and group theory .
