- Author: Olga A. Alexandrova
- Language: German
- Year: 1992
- Author: Udo Gehrmann
- Language: German
- Year: 1994
- Author: Olga Alexandroa
- Language: German
- Year: 1993
- Author: Marlis Sieburger
- Language: German
- Year: 1993
- Author: Frank Umbach
- Language: German
- Year: 1994
- Author: Peter J. Potichnyi
- Language: English
- Year: 1992
- Author: Frank Umbach
- Language: German
- Year: 1992