/usr/share/acl2-6.3/books/finite-set-theory/ is in acl2-books 6.3-5.
This file is owned by root:root, with mode 0o755.
..
/usr/share/acl2-6.3/books/finite-set-theory/osets/
/usr/share/acl2-6.3/books/finite-set-theory/osets/cardinality.o
/usr/share/acl2-6.3/books/finite-set-theory/osets/computed-hints.o
/usr/share/acl2-6.3/books/finite-set-theory/osets/delete.o
/usr/share/acl2-6.3/books/finite-set-theory/osets/difference.o
/usr/share/acl2-6.3/books/finite-set-theory/osets/instance.o
/usr/share/acl2-6.3/books/finite-set-theory/osets/intersect.o
/usr/share/acl2-6.3/books/finite-set-theory/osets/map-tests.o
/usr/share/acl2-6.3/books/finite-set-theory/osets/map.o
/usr/share/acl2-6.3/books/finite-set-theory/osets/membership.o
/usr/share/acl2-6.3/books/finite-set-theory/osets/outer.o
/usr/share/acl2-6.3/books/finite-set-theory/osets/portcullis.o
/usr/share/acl2-6.3/books/finite-set-theory/osets/primitives.o
/usr/share/acl2-6.3/books/finite-set-theory/osets/quantify.o
/usr/share/acl2-6.3/books/finite-set-theory/osets/sets.o
/usr/share/acl2-6.3/books/finite-set-theory/osets/sort.o
/usr/share/acl2-6.3/books/finite-set-theory/osets/under-set-equiv.o
/usr/share/acl2-6.3/books/finite-set-theory/osets/union.o
/usr/share/acl2-6.3/books/finite-set-theory/set-theory.o
/usr/share/acl2-6.3/books/finite-set-theory/total-ordering.o