correspondence course

I rebuilt my camera for about the twentieth time and just about finished a correspondence course in nucleonics.

Well, I never saw them danced before, so it must have been by a correspondence course.

Say,” the lad continued earnestly, “that guy never got his knowledge out of a correspondence course!

Well, by that, you mean you're still working full time but you are taking the correspondence course also?

He had earned a diploma by a correspondence course, and had scrabbled together a small practice among retired shopkeepers.