The conjugacy problem for relatively hyperbolic groups.
The cyclides of third order in pseudoisotropic space. II. (Die Zykliden 3. Ordnung im pseudoisotropen Raum. II.)
The Gauss-Bonnet theorem for Cayley-Klein geometries of dimension two.
The integrability of a field of endomorphisms
A Theorem is proved that gives intrinsic necessary and sufficient conditions for the integrability of a zero-deformable field of endomorphisms. The Theorem is proved by reducing to a special case in which the endomorphism field is nilpotent. Many arguments used in the derivation of similar results are simplified, principally by means of using quotient rather than subspace constructions.
The Martin compactification of the Cartesian product of two hyperbolic spaces.
The Projectivization of Conformal Models of Fibrations Determined by the Algebra of Quaternions
Our aim is to study the principal bundles determined by the algebra of quaternions in the projective model. The projectivization of the conformal model of the Hopf fibration is considered as example.
The satellite kinematics in Bolyai-Lobachevsky geometry in elementary geometrical representation. (Die Satellit-Kinematik in der Bolyai-Lobatschefskyschen Geometrie in elementar-geometrischer Behandlung.)
Time-like isothermic surfaces associated to Grassmannian systems.
Two models of non-Euclidean spaces generated by associative algebras