When the two were apart, they wrote each other frequent letters.

This they attempted to do with frequent letters between branches and paying close attention to exchange rates.

There were frequent open letters to public figures, and coverage of current events.

Your frequent letters of love, and encouragement will arm him with a fighting heart.

He is known for writing frequent letters to the editor in local newspapers.

Such were the recommendations of the frequent letters he wrote her.

You must make up for your absence by frequent and long letters.

I will have to make up for it with frequent (and voluminous) letters in the future.

They exchanged frequent letters, many of which have been published.

And for months her frequent letters were the most interesting aspect of my life.