On Schläfli's reduction formula.
On Schur-Ostrowski type theorems for group majorizations.
On the number of facets of three-dimensional Dirichlet stereohedra. II: Non-cubic groups.
Orbifold-Uniformizing Differential Equations. III. Arrangements Defined by 3-Dimensional Primitive Unitary Reflection Groups.
Orthogonalitätsrelationen mit Paralleleninvarianz und Zentralbündel von Schrägspiegelungen an Ebenen im äquiaffinen Raum
Orthogonality as single primitive notion for metric planes.