/usr/share/acl2-4.3/books/finite-set-theory/ is in acl2-books-source 4.3-3.
This file is owned by root:root, with mode 0o755.
..
/usr/share/acl2-4.3/books/finite-set-theory/osets/
/usr/share/acl2-4.3/books/finite-set-theory/osets/cert.acl2
/usr/share/acl2-4.3/books/finite-set-theory/osets/computed-hints.lisp
/usr/share/acl2-4.3/books/finite-set-theory/osets/fast.lisp
/usr/share/acl2-4.3/books/finite-set-theory/osets/instance.lisp
/usr/share/acl2-4.3/books/finite-set-theory/osets/map.lisp
/usr/share/acl2-4.3/books/finite-set-theory/osets/membership.lisp
/usr/share/acl2-4.3/books/finite-set-theory/osets/outer.lisp
/usr/share/acl2-4.3/books/finite-set-theory/osets/portcullis.acl2
/usr/share/acl2-4.3/books/finite-set-theory/osets/portcullis.lisp
/usr/share/acl2-4.3/books/finite-set-theory/osets/primitives.lisp
/usr/share/acl2-4.3/books/finite-set-theory/osets/quantify.lisp
/usr/share/acl2-4.3/books/finite-set-theory/osets/set-order.lisp
/usr/share/acl2-4.3/books/finite-set-theory/osets/sets.lisp
/usr/share/acl2-4.3/books/finite-set-theory/osets/sort.lisp
/usr/share/acl2-4.3/books/finite-set-theory/set-theory.acl2
/usr/share/acl2-4.3/books/finite-set-theory/set-theory.lisp
/usr/share/acl2-4.3/books/finite-set-theory/total-ordering.lisp