Tactical decompositions of designs.
Tangents of conics in Hjelmslev planes over a local ring of even characteristic
Teilmengengraphen und projektive Räume.
Ternary linear codes and quadrics.
Ternary rings of Pappian planes
Ternary rings with zero associated to Desarguesian and Pappian planes
Ternary rings with zero associated to translation planes
The affine plane AG(2,q), q odd, has a unique one point extension.
The chromatic index of cyclic Steiner 2-designs.
The classification of generalized quadrangles with two translation points.
The classification of SPG-systems of index 2.
The classification of spreads in admitting linear groups of order . II: Even order.
The Coexistence of Elations and Homologies.
The Collineation Groups of Derived Translation Planes. II.
The cross-ratio in Hjelmslev planes
The cross-ratio in Hjelmslev planes is defined. The cross-ratio in the Hjelmslev plane is independent of the choice of a coordinate system on a line.
The cyclic -clans with .
The finite Moufang hexagons coordinatized.
The four known biplanes with k=11.
The fundamental theorem for the projective line over commutative rings. (Short Communication).
The fundamental theorem for the projective line over commutative rings.