Maybe I should clarify that I didn't start the thread in order to criticize Dylan for his musical borrowing or his laxness in identifying his sources. I just wanted some help verifying the source-identifications I found on another web site. I'm glad the thread has evolved into a discussion the practicalities and etiquette of musical borrowing, but it wasn't the founding motivation.
A good bibliography of scholarly studies of musical borrowing is here. There's no mention of Dylan (or much of any 20th-century popular music) but you still get some fascinating citations if you type "folk" or "contrafactum" (or "contrafacta") in their site-search engine.
T.