von O’Reilly als PDF zum freien Download. Zwar sind überall im PDF häßliche Ausschußmarken zu sehen, aber man will sich das Teil ja nicht unbedingt binden lassen. „The most complete book on the Asterisk PBX system to date. The new book, announced at Astricon 2005 covers many of the new features of Asterisk 1.2. In the spirit of open source, O’Reilly has licensed the book under the creative commons license making it free to download and distribute. If you are looking for the ultimate Asterisk book, you can now download the entire book as a PDF file!“ (voipspeak.net)