- Author: Michael Knapp
- Language: English
- Year: 2017
- Author: Michael Knapp
- Language: English
- Year: 2017
- Author: Michael Knapp Ring
- Language: Spanish
- Year: 2008
- Author: Michael Knapp
- Language: English
- Year: 2018
- Author: Anja Flach Ercan Ayboga Michael Knapp
- Language: German
- Year: 2015
- Author: Michael Knapp (auth.)
- Language: German
- Year: 2002