The man who was the source of his problems, and always had been.

Let's look first at the system as the source of the problem, he says.

He was known for looking beyond the end result to find the source of the problem.

They had to go to the source of the problem.

How about we go after the source of the problem for a change?

He started to type, looking for the source of the problem.

Even though the numbers may be similar, the source of the problem is different.

"I sent him looking for the source of the problem, but he came up with you!"

But we have not identified the source of the problem yet.

The only place to take it was where the source of the problem lay.