Nathan Bransford - The Forums

I apologize if something similar has been asked before --

Is it okay to quote a line of, say, Shakespeare or Poe in a mystery as a clue, with the assumption that it will be acknowledged at some point that it is a line from one of their poems?

I think so. I'd check and see if these two have fallen into public domain. I am pretty sure that Shakespeare is. Not so sure about Poe.

I'm not a publishing attorney so take my opinion with a grain of salt, but if the work is in the public domain you don't have to clear permission. If it is under copyright you do.