/usr/share/acl2-6.5/books/coi/osets/ is in acl2-books-source 6.5-2.
This file is owned by root:root, with mode 0o755.
..
/usr/share/acl2-6.5/books/coi/osets/cert.acl2
/usr/share/acl2-6.5/books/coi/osets/computed-hints.lisp
/usr/share/acl2-6.5/books/coi/osets/conversions.lisp
/usr/share/acl2-6.5/books/coi/osets/extras.lisp
/usr/share/acl2-6.5/books/coi/osets/fast.lisp
/usr/share/acl2-6.5/books/coi/osets/instance.lisp
/usr/share/acl2-6.5/books/coi/osets/listsets.lisp
/usr/share/acl2-6.5/books/coi/osets/map.lisp
/usr/share/acl2-6.5/books/coi/osets/membership.lisp
/usr/share/acl2-6.5/books/coi/osets/multiappend.lisp
/usr/share/acl2-6.5/books/coi/osets/multicons.lisp
/usr/share/acl2-6.5/books/coi/osets/outer.lisp
/usr/share/acl2-6.5/books/coi/osets/primitives.lisp
/usr/share/acl2-6.5/books/coi/osets/quantify.lisp
/usr/share/acl2-6.5/books/coi/osets/set-order.lisp
/usr/share/acl2-6.5/books/coi/osets/set-processor.lisp
/usr/share/acl2-6.5/books/coi/osets/sets.lisp
/usr/share/acl2-6.5/books/coi/osets/sort.lisp