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