The sea has always been the only source of food and money.

Children are many parents' only source of security in old age.

Track and Field has been the only source of success for the nation.

She was the only source of information they had, and he couldn't risk her.

They were once the only source of water to the city.

It was the only source of light in the room.

A third says they should not be the only source of information about a school.

But this was not the only source of light below.

We are not saying this should be the only source.

Their only source of knowledge about Europe and the world is television.