Irreducible factors of Psi-Polynomials over finite fields. Ulrich Schoenwaelder — 1988 Manuscripta mathematica
A Characterization of the Simple Group M24. Ulrich Schoenwaelder; Dieter Held — 1970 Mathematische Zeitschrift
The Core-Free Groups of Sylow-2-type M24. Hedwig Sandlöbes; Ulrich Schoenwaelder — 1979 Mathematische Zeitschrift