Reformatio Sigismundi

There was an error in the original text of lecture 19, which said: "The reformatio sigismundi, a pamphlet produced in 1439 on one of Gutenberg's new printing presses ..." Gutenberg's invention was not complete until 1455. I corrected the text to "The reformatio sigismundi, a pamphlet produced in 1439, printed in 1476 on one of Gutenberg's new printing presses, reprinted seven times and distributed throughout Germany ..."