fair use rules (as each use requires a separate analysis).
What if You Get Signed to a Big Deal Publisher? If you're planning to sign with a commercial publisher then things could get more complicated because most publishers will require that you clear copyrighted materials beforehand -- they're not big fair use fans. And they'll insist that you indemnify them as well. Which means that if they get sued, you'll pay for their legal costs. Ouch! So, if you're looking at a commercial publishing deal take your questions to a copyright lawyer for an expert opinion on each use. Then, you can proceed with more confidence if you need to indemnify.