He closed his eyes for a moment and frowned in concentration.

She looked down her small, straight nose at me, frowning in concentration.

The little man frowned in concentration as he examined it.

He thought this over for a moment, frowning in concentration.

Toby would have frowned in concentration if he'd been able to.

He pushed the hair out of his eyes and frowned in concentration.

For a moment, he looked at the changed mirror, frowning in concentration.

She kept singing for a while, frowning in concentration, ignoring him.

"This is getting a little complicated," Bill said, frowning in concentration.

She took the first one and looked at it, frowning in concentration.