Columbia subject headings:
Fisheries--Baltic Sea.
Geology--Baltic Sea.
Marine biology--Baltic Sea.
Marine pollution--Baltic Sea.
Oceanography--Baltic Sea.
Harvard subject headings:
Fisheries--Baltic Sea.
Geology--Baltic Sea.
Marine biology--Baltic Sea.
Marine pollution--Baltic Sea
Oceanography--Baltic Sea.
Princeton subject headings:
Fisheries--Baltic Sea.
Geology--Baltic Sea.
Marine biology--Baltic Sea.
Marine pollution--Baltic Sea.
Oceanography--Baltic Sea.