Columbia subject headings:
Harvard subject headings:
Espionage, East German--History.
Germany (East). Ministerium für Staatssicherheit--History.
Internal security--Germany (East)--History.
Sorbs--Germany (East)--History.
Princeton subject headings:
Espionage, East German--History.
Germany (East). Ministerium für Staatssicherheit--History.
Sorbs--Germany--History.