On a certain triangle transformation and some of its applications.
On a class of hyperplanes of the symplectic and Hermitian dual polar spaces.
On a class of partial -spreads of arising from scrolls.
On a dependence between polarities and an order of a projective plane
On a functional equation arising from hyperbolic geometry.
On a general principle in geometry that leads to functional equations.
On a generalization of nets
On a Generalization of the Gallai-Sylvester Theorem.
On a generalized Minkowski inequality and its relation to dominates for t-norms.
On a generalized stereographic projection. (Zur verallgemeinerten stereographischen Projektion.)
On a geometric inequality by J. Sándor.
On a Model of Plane Geometry.
On a Paschian Condition for Linear Spaces.
On a planar construction of quasigroups
On a problem for isometric mappings of posed by Th. M. Rassias.
On a quasilinear elliptic equation and a Riemannian metric invariant under Möbius transformations.
On a quasilinear elliptic equation and a Riemannian metric invariant under Möbius transformations. (Summary).
On a special class of Frobenius groups admitting planar partitions.
On a system of equations related to bicentric polygons.
On affine planes non-extensible to Laguerre planes and some related problems
Some examples of affine planes non-extensible to a Laguerre plane are studied and conditions for the uniqueness of a Laguerre extension are given.