He glanced down at her once in a while.

She willed him to turn back, to look at her once.

We must approach him sooner or later, for he is the staple of what I have to say, and it's as well at once.

The narrator gets dressed and leaves for the doctor's home at once.

Not the kind he would have looked at even once, back on Earth with his million-dollar retirement fund.

The woman glanced at her once, then looked straight ahead.

He looked over his shoulder at her once, and she turned away.

The Speaker realized his son had never seen so many people before at once.

He'd looked at her once, so that she'd nearly wavered.

Lauren, busy making notes, realized he hadn't looked at her once.