[Currently Under Progress. This will mainly be a place for old Volapük books.]
[1880] Volapük, die Weltsprache [Google Books]
[1884] Volapük (Weltsprache): Grammatik der Universalsprache für alle gebildete Erdbewoner [Dritte Auflage ❦ Third Edition] [Google Books]
[1884] Volapük (Weltsprache): Grammatik der Universàlspràche für alle gebíldete Erdbewòner [Vierte Auflage ❦ Fourth Edition] [Google Books]
[1887] Grammar with Vocabularies of Volapük: (the Language of the World) for All Speakers of the English Language [Second Edition] [Google Books]
[1888] Volapük: An Easy Method of Acquiring the Universal Language [Google Books]
[1889] Dictionary of Volapük: Volapük-English, English-Volapük [Google Books]