4-dimensionale Translationsebenen.
A note on embedding and generating dual polar spaces.
A Poncelet theorem in space.
A Resolution of the Sylvester-Gallai Problem of J.-P. Serre.
Algebraische Geometrien
Central Automorphisms of Veblenian Nearaffine Planes
The paper deals with nearaffine planes described by H. A. Wilbrink. We consider their central automorphisms, i.e. automorphisms satisfying the Veblen condition, which become central collineations in connected projective planes. Moreover, a concept of central pseudo-automorphism is considered, i.e. some bijections in a nearaffine plane are not automorphisms but they become central collineations in the related projective planes.
Characterization of epimorphisms of nets by normal decompositions
Classical polar spaces (sub-)weakly embedded in projective spaces.
Closure conditions in the nets
Die klassisch-projektive Natur der Kettengeometrien endlicher Dimensionen.
Dual partial quadrangles embedded in .
Dualitäten mit zwei Geraden aus absoluten Punkten in projektiven Ebenen.
Ein "affiner" Beweis des Satzes von v. Staudt - Schleiermacher.
Eine geometrische Kennzeichnung linearer Abbildungen.
Eine Verallgemeinerung des Satzes von Dandelin.
Embeddings of projective Klingenberg planes in the projective space PG(5,).
Extending Nearaffine Planes to Hyperbola Structures
H. A. Wilbrink [Geom. Dedicata 12 (1982)] considered a class of Minkowski planes whose restrictions, called residual planes, are nearaffine planes. Our study goes in the opposite direction: what conditions on a nearaffine plane are necessary and sufficient to get an extension which is a hyperbola structure.
Flags in Euclidean three-space.
Generating symplectic and Hermitian dual polar spaces over arbitrary fields nonisomorphic to .
Geraden-Abbildungen, die den Flächeninhalt 1 von Dreiecken erhalten.