Columbia subject headings:
Crimea (Ukraine)--Description and travel.
Danube River--Description and travel.
Natural history--Ukraine--Crimea.
Romania--Description and travel.
Russia--Description and travel.
Harvard subject headings:
Crimea (Ukraine)--Description and travel.
Danube River--Description and travel.
Natural history--Ukraine--Crimea.
Romania--Description and travel.
Russia--Description and travel.
Soviet Union--Description and travel.
Princeton subject headings: