For most of this course the river forms the boundary between the two countries.

It forms the international boundary between the two countries for much of its length.

For much of its length it forms the international boundary between the two countries.

The two points a and b form the boundary of the open interval.

The river and its wetlands form the complex's southern boundary.

Its lower length forms the eastern boundary of the city.

Private land to the west of Route 73 forms the eastern boundary.

Flowing generally south, it forms the international boundary for around 6 miles.

The river channel forms the eastern boundary of the bank.

To the south, the state border with California forms the boundary of the forests.