Some professors in the Uni I attended are enlightened and use open textbooks. One thou amazed me. He taught Discreet Math. He had every edition of the book f

Some professors in the Uni I attended are enlightened and use open textbooks. One thou amazed me. He taught Discreet Math. He had every edition of the book for the last 10 years and told us to bring any one of them. He had a map for the homework shuffle between editions and alerted us to the little changes made in the text itself. Gem of a teacher.