1. Quaternionic-like structures on a manifold I;Alekseevskii;Rend. Mat. Acc. Lincei,1993
2. Quaternionic-like structures on a manifold II;Alekseevskii;Rend. Mat. Acc. Lincei,1993
3. Einstein Manifolds;Besse,1987
4. Reflections in contact geometry;Bueken,1989
5. Reflections and rotations in contact geometry, doctoral dissertation;Bueken,1992