Ug. Spending part of my day today trying to help authors track down some permissions (this is one of the least fun parts of putting a book together). It’s important to get all of your permissions in order if you excerpt a portion of another work in your book (including other books, songs, poems…).
A bit of advice to writers: most publishers put the responsibility for obtaining permission to use an excerpt on the author (meaning you have to track this stuff down yourself and pay any necessary fees). I advise most authors to try to keep their excerpt length down to fall within the realm of “fair use.”