Ein gruppentheoretischer Aufbau der räumlichen äquiaffinen Geometrie unter Verwendung von Scherungen
Eine Verallgemeinerung des Satzes von Dandelin.
Elementary versions of the Sylvester-Gallai theorem.
Entartete Steinerkegelschnitte in nichtpapposschen Desarguesebenen.
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.
Extension of Collineations Defined on Certain Sets of a Desarguesian Projective Plane