/usr/share/doc/gir1.2-gtk-3.0/AUTHORS is in gir1.2-gtk-3.0 3.18.9-1ubuntu3.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/gir1.2-gtk-3.0/../libgtk-3-0/AUTHORS
/usr/share/doc/gir1.2-gtk-3.0/../libgtk-3-0/AUTHORS