- Author: J. Baumann
- Language: German
- Year: 1908
Der wahlweise Anruf in Telegraphen- und Telephonleitungen und die Entwicklung des Fernsprechwesens
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- Author: J. Baumann
- Language: German
- Year: 1904
- Author: D. Mazzotto, J. Baumann
- Language: German
- Year: 1906
- Author: S. Jellinek
- Language: German
- Year: 1906
- Author: Curt Grimm
- Language: German
- Year: 1908