Columbia subject headings:
Harvard subject headings:
Düffel, John von--Stage history.
Düffel, John von. Leben des Siegfried.
Nibelungenlied.
Siegfried (Legendary character)--In literature.
Theater--Production and direction.
Princeton subject headings:
Düffel, John von--Stage history.
Düffel, John von. Leben des Siegfried.
Nibelungenlied.
Siegfried (Legendary character) in literature.
Theater--Production and direction.