- Author: Otto Janssen
- Language: German
- Year: 1933
- Author: Otto Janssen
- Language: German
- Year: 1932
- Author: Olga Janssen
- Language: German
- Year: 1984
- Author: Theo Janssen (editor), Gisela Redeker (editor)
- Language: English
- Year: 1999
- Author: C. W. Janssen
- Language: German
- Year: 1886
- Author: J. M. A. Janssen, K. Schefold, V. D. Blavatskij, Carl Weickert
- Language: German
- Year: 1950