Near hexagons with four points on a line.
Necessary and sufficient conditions for the existence of -chordal polygons.
Note on span-symmetric generalized quadrangles.
On equations and properties concerning some classes of chordal polygons.
On flocks of infinite quadratic cones.
On -chordal polygons.
On ovoids of .
On -clan geometry, .
On some flag-transitive non-classical -geometries. II.
On the history of generalized quadrangles.
On the size of maximal caps in .
Plane models of semi-biplanes.
Pseudodual grids and extensions of generalized quadrangles.
Pseudo-ovals, elation Laguerre planes, and translation generalized quadrangles.
Quadratische Identitäten bei Polygonen.
Regular partial conical flocks.
Some inequalities concerning the existence of -chordal polygons.
Split semi-biplanes in antiregular generalized quadrangles.
Strongly regular locally -graphs.
Subgroups of the Chevalley groups of type arising from a polar space.