ALPERIN-BRAUER-GORENSTEIN THEOREM

In mathematics, the 'Alperin--Brauer--Gorenstein theorem' characterizes the finite simple groups with quasidihedral or wreathed Sylow 2-subgroups. These are isomorphic either to three-dimensional projective special linear or projective special unitary groups over a finite fields of odd order,
depending on a certain congruence, or to the Mathieu group $M\_\{11\}$.