The country's summer league has also proved a vital source of player development.

Tourism has in recent decades become a vital source of income.

It is a vital source of financial and technical assistance to developing countries around the world.

The southern riverbank was a vital source of their food and living resources.

Indeed, we have been a vital source of money in these recessionary times.

Coal was the most vital source of energy at that time.

This is an important way we can continue serving our readers, and remain a vital source of information in the Internet age.

The river is a vital source to grazing animals nearby.

The money they send home has become a vital source of income here.

Indian Point is a vital source of power in the region.