Columbia subject headings:
Danube River Delta (Romania and Ukraine)--Commerce--History--19th century.
Danube River--Navigation--History--19th century.
Eastern question (Balkan)
Moldavia--Foreign economic relations.
Wallachia--Foreign economic relations.
Harvard subject headings:
Danube River Delta (Romania and Ukraine)--Commerce--History--19th century.
Danube River Delta (Romania and Ukraine)--Economic aspects--19th century.
Danube River Delta (Romania and Ukraine)--Navigation--19th century.
Danube River--Navigation--History--19th century.
Eastern question (Balkan)
Moldavia--Foreign economic relations.
Wallachia--Foreign economic relations.
Princeton subject headings: