He looked around, trying to determine the source of the light.

He said that in several cases, the source of the threat could not be determined.

He added that the government should determine the source of the $5.6 billion, because it was "a political matter."

It is important to attempt to determine the source of the problem.

It was not possible to determine the source of the light in the sky.

We have, however, determined the source of their power and believe it or not the enemy is us.

The police have not determined the source of the false reports.

It is often difficult even to determine the source of infection.

Using this approach, however, the sources of uncertainty cannot be determined.

The source of infection in these individuals has not been determined.