Luft, Kathleen (1988). "National Security". In Burant, Stephen R. (ed.). East Germany: a country study. Area Handbook (3rd ed.). Washington, D.C.: Library of Congress. pp. 264–265. LCCN87600490. Retrieved 19 October 2021.
lccn.loc.gov
Luft, Kathleen (1988). "National Security". In Burant, Stephen R. (ed.). East Germany: a country study. Area Handbook (3rd ed.). Washington, D.C.: Library of Congress. pp. 264–265. LCCN87600490. Retrieved 19 October 2021.