On pairs of metrics invariant under a cocompact action of a group.
On permutable quadratic inversions in plane with two common singular points
On perspectivities in incidence geometries of grade n
On Planes of Lenz-Barlotti Class I 6 and Planes of Lenz Class III.
On Polyhedra with Transitivity Properties.
On projective planes of order 20
On Projective Planes of Order Twelve and Twenty.
On Projective Planes of Type (5, m).
On propellers from triangles.
On pythagorean angles
On -clan geometry, .
On rainbowness of semiregular polyhedra
We introduce the rainbowness of a polyhedron as the minimum number such that any colouring of vertices of the polyhedron using at least colours involves a face all vertices of which have different colours. We determine the rainbowness of Platonic solids, prisms, antiprisms and ten Archimedean solids. For the remaining three Archimedean solids this parameter is estimated.
On rank 2 geometries of the Mathieu group .
On Rank 3 Projective Designs.
On rank 4 projective planes.
On rank 5 projective planes.
On rational Morley triangles
On Rusakov’s -ary -groups
Properties of -ary groups connected with the affine geometry are considered. Some conditions for an -ary -group to be derived from a binary group are given. Necessary and sufficient conditions for an -ary group -derived from an additive group of a field to be an -group are obtained. The existence of non-commutative -ary -groups which are not derived from any group of arity for every , is proved.
On S. Gołąb's characterization of the anharmonic ratio
On Schläfli's reduction formula.