But in the middle of October his letters and messages suddenly changed.

Nor was he surprised that the yellow letters on the screen had changed to red.

The call letters, however, have not changed since 1987.

Although the station reverted to sports talk a year later, the call letters did not change.

The circle of magnets was the same, but the letters inside had changed.

Documents and letters changed while they looked at them, yet they did learn a little.

The call letter changed marked a change in programming from primarily classical music.

His mood changed as he heard Roger's story, and the letter changed.

While the letters do not change the general picture of the epidemic, they offer new details and give the events immediacy.

The first clue came from the British, who had noticed that the code's letters did not change randomly.