Copyright © 2019 Ricardo Wurmus

Copyright © 2019 Efraim Flashner

Copyright © 2019 Pierre Neidhardt

Copyright © 2020 Oleg Pykhalov

Copyright © 2020 Matthew Brooks

Copyright © 2020 Marcin Karpezo

Copyright © 2020 Brice Waegeneire

Copyright © 2020 André Batista

Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.  A copy of the license is included in the section entitled ``GNU Free Documentation License''.