- Author: Wilhelm Johnen
- Language: English
- Year: 2018
- Author: Wilhelm Johnen
- Language: English
- Year: 2018
- Author: Ute Ehrhardt Wilhelm Johnen
- Language: Hungarian
- Year: 2013
- Author: Ute Ehrhardt Wilhelm Johnen
- Language: Hungarian
- Year: 2013
- Author: Ute Ehrhardt Wilhelm Johnen
- Language: Hungarian
- Year: 2013