He had never been so tired before that merely looking into somebody's heartfire felt like an impossible burden to him.

He gave a long sigh as though I had saddled him with some impossible burden.

Yet he would have been an impossible burden for a pony through the drifts.

It's an impossible burden for us to take on.

Would it really be an impossible burden to stop every moral outrage on the level of Kosovo?

What the interest groups say they fear, however, is that this line of reasoning could create an impossible burden for online video sharing.

The sense of guilt must be an impossible burden.

Last week the appeals court made the prosecution's burden all but impossible.

A mother of two, with a full-time job and part-time school classes, she saw a fourth child as an impossible burden.

In moments the axe began to seem an impossible burden.