/usr/share/acl2-7.1/books/std/osets/ is in acl2-books-source 7.1-1.
This file is owned by root:root, with mode 0o755.
..
/usr/share/acl2-7.1/books/std/osets/cardinality.lisp
/usr/share/acl2-7.1/books/std/osets/cert.acl2
/usr/share/acl2-7.1/books/std/osets/computed-hints.lisp
/usr/share/acl2-7.1/books/std/osets/delete.lisp
/usr/share/acl2-7.1/books/std/osets/difference.lisp
/usr/share/acl2-7.1/books/std/osets/element-list.lisp
/usr/share/acl2-7.1/books/std/osets/instance.lisp
/usr/share/acl2-7.1/books/std/osets/intersect.lisp
/usr/share/acl2-7.1/books/std/osets/map-tests.lisp
/usr/share/acl2-7.1/books/std/osets/map.lisp
/usr/share/acl2-7.1/books/std/osets/membership.lisp
/usr/share/acl2-7.1/books/std/osets/outer.lisp
/usr/share/acl2-7.1/books/std/osets/primitives.lisp
/usr/share/acl2-7.1/books/std/osets/quantify.lisp
/usr/share/acl2-7.1/books/std/osets/sort.lisp
/usr/share/acl2-7.1/books/std/osets/top.lisp
/usr/share/acl2-7.1/books/std/osets/under-set-equiv.lisp
/usr/share/acl2-7.1/books/std/osets/union.lisp