- Author: Karl Völker
- Language: German
- Year: 1930
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- Language: German
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- Language: German
- Year: 1925
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- Language: German
- Year: 1961
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- Language: German
- Year: 1926
- Author: Dmitrij Zelenin
- Language: German
- Year: 1927
- Author: Bogdan Filov
- Language: German
- Year: 1933
- Author: Nicolaas Wijk
- Language: German
- Year: 1931
- Author: Demetrius Ainalov
- Language: German
- Year: 1933
- Author: Bogdan Dimitrov Filov
- Language: German
- Year: 1932