- Author: Stanislav Grof
- Language: German
- Year: 2017
- Author: D. M. Turner
- Language: German
- Year: 1994
- Author: Leary Timothy
- Language: German
- Year: 1997
- Author: Grotenhermen Franjo, Reckendrees Britta
- Language: German
- Year: 2016
- Author: Derix Govert H.M., Kuby Christiane
- Language: German
- Year: 2004
- Author: Timothy Leary
- Language: German
- Year: 1997
- Author: Roberto Torretti Bert Marco Schuldes
- Language: German
- Year: 1999
- Author: Bert Marco Schuldes
- Language: German
- Year: 1997
- Author: Markus Berger
- Language: German
- Year: 2004
- Author: Jochen Gartz
- Language: English
- Year: 1998