All the books are published under the terms of the
[CC-BY-SA](https://creativecommons.org/licenses/by-sa/4.0/) license and have
been published in various formats: paperback, web and an easy to print PDF
file, with the goal of making them available for anyone.

Digital versions of the books are available in the list below while the
paperback edition can be obtained [contacting
us](mailto:publishing@elenq.tech).

For those who want to take part in the development, send comments, propose
corrections or even create derivative works, having the sources is more than
interesting. Each book has a link to its Git repository where raw content,
change history, etc. are available.