No public mention of this book was made, perhaps because if the enemy had heard of its existence they would have modified their tactics and dispositions.

That was how I first heard of your existence.

First I've heard of your existence was a few days ago, when Dr. Volin got a message to me.

According to him, he and his fellow resistance members had not even heard of their existence.

Rolf had heard of Charmian's existence, but had not really thought about her until now.

The factory inspectorate has never heard of their existence.

He was so well insulated that it took law-enforcement authorities several years to hear of his existence.

He had heard of its existence when he was a young man.

I never heard of her existence till the day before yesterday.

They are just the very Selenites who'll never have heard of our existence.