(see [https://btrfs.wiki.kernel.org/index.php/Main_Page btrfs@kernel.org], [https://btrfs.readthedocs.io/en/latest/ btrfs.readthedocs.io], [https://wiki.archlinux.org/title/Btrfs Btrfs@ARC-wiki], [https://de.wikipedia.org/wiki/Btrfs Btrfs@wikipedia])
(see btrfs@kernel.org, btrfs.readthedocs.io, Btrfs@ARC-wiki, Btrfs@wikipedia)