If I give credit can I put a famous quote on T-shirts I sell?
NO. That is usually counterproductive. The author is often a celebrity or famous enough to have rights of publicity that you may violate by using the name or likeness commercially. You also need to determine that you can use the quote in the first place. See my legal guide for that question at https://www.avvo.com/legal-guides/ugc/can-i-use-famous-quotes-on-my-products-without-permission Just using the quote reduces the risk of copyright infringement. WARNING. Be sure the quote is not a trademark, such as a famous advertising slogan. To check you might look here http://goo.gl/c4qJV (http://goo.gl/c4qJV) See a licensed attorney.