I was thumbing through a copy (just glancing, really) of Dumas' The Three Musketeersat my local library, and noticed that there was a scene where a letter was in possession of one of the characters that granted its bearer the full authority of its author. That looked *awfully* familiar--rather like a device Jordan used in books 3 and 4 with the letter from Siuan Sanche. I wonder if Jordan picked that up from Dumas...

It is a pretty common element to have something like that.