Columbia subject headings:
Harvard subject headings:
Kattegat (Denmark and Sweden)--International status.
Skagerrak--International status.
Sound, The (Denmark and Sweden)--International status.
Straits--Denmark
Straits--Norway.
Straits--Sweden.
Princeton subject headings:
Kattegat (Denmark and Sweden)--International status.
Skagerrak--International status.
Sound, The (Denmark and Sweden)--International status.