- Author: Ragnar Arntzen, Gisela Håkansson, Arnstein Hjelde, Jörg-U. Keßler
- Language: English
- Year: 2019
- Author: Jörg-U. Keßler, Anke Lenzing, Mathias Liebner
- Language: English
- Year: 2016
- Author: Jörg-U. Keßler, Dagmar Keatinge
- Language: English
- Year: 2009