- Author: Peter Pepper Petra Hofstedt (auth.)
- Language: German
- Year: 2006
- Author: Petra Hofstedt (auth.)
- Language: English
- Year: 2011
- Author: Petra Hofstedt (auth.)
- Language: English
- Year: 2011
- Author: Petra Hofstedt (auth.)
- Language: English
- Year: 2011
- Author: Petra Hofstedt (auth.)
- Language: English
- Year: 2011