/usr/share/acl2-8.0dfsg/books/centaur/clex/ is in acl2-books-source 8.0dfsg-1.
This file is owned by root:root, with mode 0o755.
..
/usr/share/acl2-8.0dfsg/books/centaur/clex/arithmetic.lisp
/usr/share/acl2-8.0dfsg/books/centaur/clex/cert.acl2
/usr/share/acl2-8.0dfsg/books/centaur/clex/charlist-fix.lisp
/usr/share/acl2-8.0dfsg/books/centaur/clex/example.lisp
/usr/share/acl2-8.0dfsg/books/centaur/clex/linecol.lisp
/usr/share/acl2-8.0dfsg/books/centaur/clex/matchers.lisp
/usr/share/acl2-8.0dfsg/books/centaur/clex/portcullis.acl2
/usr/share/acl2-8.0dfsg/books/centaur/clex/portcullis.lisp
/usr/share/acl2-8.0dfsg/books/centaur/clex/sin.lisp
/usr/share/acl2-8.0dfsg/books/centaur/clex/strin.lisp
/usr/share/acl2-8.0dfsg/books/centaur/clex/top.lisp