This book was written by Fabio Cevasco and it is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License.
This book was authored using Glyph and the PDF version was produced with Prince XML.
The Ruby logo is copyright © 2006, Yukihiro Matsumoto, and used under the terms of the Creative Commons Attribution-ShareAlike 2.5 License.
Special thanks to the following individuals who contributed to the project, in some ways: