Columbia subject headings:
Harvard subject headings:
Cargo ships--Germany--History.
Deutsche Seereederei Rostock--History.
Merchant marine--Germany (East)--History.
Merchant marine--Germany--History.
Shipping--Germany (East)--History.
Princeton subject headings:
Cargo ships--Germany--History.
Deutsche Seereederei Rostock--History.
Merchant marine--Germany (East)--History.
Merchant marine--Germany--History.
Shipping--Germany (East)--History.