Creative Commons and the Four-to-Free (42F) Guarantee

Each CommonsWare book version will be available for use under the Creative Commons Attribution-Noncommercial-ShareAlike 3.0 license as of the fourth anniversary of its publication date. That means that, once four years have elapsed, you can use this prose for non-commercial purposes. That is our Four-to-Free Guarantee to our readers and the broader community.

This edition of this book will be available under the aforementioned Creative Commons license on 1 October 2025.

For more details on the Creative Commons Attribution-Noncommercial-ShareAlike 3.0 license, visit the Creative Commons Web site

Note that future editions of this book will become free on later dates, each four years from the publication of that edition. Releasing one edition under the Creative Commons license does not automatically release all editions under that license.