Columbia subject headings:
Harvard subject headings:
Esperanto--History.
Languages, Artificial--History.
Schleyer, Johann Martin, 1831-1912
Volapük--History.
Zamenhof, L. L. (Ludwik Lazar), 1859-1917.
Princeton subject headings:
Esperanto--History.
Languages, Artificial--History--19th century.
Schleyer, Johann Martin, 1831-1912.
Volapük--History.
Zamenhof, L. L. (Ludwik Lazar), 1859-1917.