/usr/share/acl2-8.0dfsg/books/kestrel/apt/ is in acl2-books-source 8.0dfsg-1.
This file is owned by root:root, with mode 0o755.
..
/usr/share/acl2-8.0dfsg/books/kestrel/apt/cert.acl2
/usr/share/acl2-8.0dfsg/books/kestrel/apt/portcullis.acl2
/usr/share/acl2-8.0dfsg/books/kestrel/apt/portcullis.lisp
/usr/share/acl2-8.0dfsg/books/kestrel/apt/restrict-design.lisp
/usr/share/acl2-8.0dfsg/books/kestrel/apt/restrict-reference.lisp
/usr/share/acl2-8.0dfsg/books/kestrel/apt/restrict-tests.lisp
/usr/share/acl2-8.0dfsg/books/kestrel/apt/restrict.lisp
/usr/share/acl2-8.0dfsg/books/kestrel/apt/tailrec-design.lisp
/usr/share/acl2-8.0dfsg/books/kestrel/apt/tailrec-reference.lisp
/usr/share/acl2-8.0dfsg/books/kestrel/apt/tailrec-tests.lisp
/usr/share/acl2-8.0dfsg/books/kestrel/apt/tailrec.lisp
/usr/share/acl2-8.0dfsg/books/kestrel/apt/top.lisp
/usr/share/acl2-8.0dfsg/books/kestrel/apt/utilities/
/usr/share/acl2-8.0dfsg/books/kestrel/apt/utilities/cert.acl2
/usr/share/acl2-8.0dfsg/books/kestrel/apt/utilities/print-specifiers-tests.lisp
/usr/share/acl2-8.0dfsg/books/kestrel/apt/utilities/print-specifiers.lisp
/usr/share/acl2-8.0dfsg/books/kestrel/apt/utilities/top.lisp
/usr/share/acl2-8.0dfsg/books/kestrel/apt/utilities/transformation-table-tests.lisp
/usr/share/acl2-8.0dfsg/books/kestrel/apt/utilities/transformation-table.lisp