http://www.loc.gov/mods/v3 http://www.loc.gov/standards/mods/v3/mods-3-2.xsd
music drama in three acts (from the trilogy Der ring des Nibelungen)
by Richard Wagner ; English version by Stewart Robb.
Libretto in German and English; accompanying text in English.
From the Edward O. D. Downes Collection.
G. Schirmer's collection of opera librettos