Columbia subject headings:
German literature--19th century--History and criticism.
Mermaids in literature.
Water spirits in literature.
Harvard subject headings:
German literature--19th century--History and criticism
Mermaids in literature.
Opera--Germany--19th century.
Undine (Tale)
Water spirits in literature.
Princeton subject headings:
German literature--19th century--History and criticism.
Opera--Germany--19th century.
Undine (Legendary character)--In literature.