sentences:  Stein manifolds and Stein factorization are named after him.Karl Stein received his doctorate with his dissertation on the topic "Zur Theorie der Funktionen mehrerer komplexer Veränderlichen; Die Regularitätshüllen niederdimensionaler Mannigfaltigkeiten" at the University of Münster under the supervision of Heinrich Behnke in 1937.Karl Stein was conscripted into the Wehrmacht sometime before 1942, and trained as a cryptographer to work at OKW/Chi, the Cipher Department of the High Command of the Wehrmacht.