If you let a character quote someone/something (book, something a person said, a song etc...) and you mention who said/wrote/made it, can you use it without any other trouble? I was considering giving one of my characters a notebook full of such quotes that he carries around the whole time and perhaps share them with the people who accompany him on his journey. Example: "Hope is the thing with feathers that perches the soul," he said. "Hope is a bird?" "Perhaps," he smiled. "It's from a poem by Emily Dickinson"