Katherine had a feeling that she had seen it before somewhere.

George felt sure she had seen him before somewhere.

Actually, I think that 1ac is an old clue - seem to remember seeing it before somewhere.

Watch for people you've seen before somewhere, in the street, in the shops.

He stopped, feeling uneasy, for he was sure he'd seem him before somewhere.

He paused to think; he'd seen this kind of thing before somewhere in his travels.

Again she was sure that she had seen those eyes before somewhere.

He had heard the simile before somewhere in another form.

He grew aware that the woman was speaking: 'I seem to have seen him before somewhere.

"I'm sure I've heard that name before somewhere, but I can't place it."