Columbia subject headings:
Ice breaking operations--Polar regions.
Ice-breaking vessels--United States.
United States. Coast Guard--Ice breaking operations.
Harvard subject headings:
Ice breaking operations--Polar regions.
Icebreakers (Ships)--United States.
United States. Coast Guard--Ice breaking operations.
Princeton subject headings:
Ice breaking operations--Polar regions.
Icebreakers (Ships)--United States.
United States. Coast Guard--Ice breaking operations.