How do I obtain permission, and what do I do with it?

Contact the copyright holder and explain what work you wish to use and for what purpose. Request their written permission for you to use the material in publication. Some copyright holders will provide permission for free and others will charge a fee. If you cannot get a reply after several attempts, you may be able to use the material without permission, but make sure to keep all documented instances of failed attempts and consult a legal professional to be sure.

Keep the written permission in your possession if for any reason you should need to prove permission in the future. The copyright holder may or may not require additional credit in the book itself.