/usr/share/acl2-6.3/books/xdoc/ is in acl2-books-source 6.3-5.
This file is owned by root:root, with mode 0o755.
..
/usr/share/acl2-6.3/books/xdoc/all.lisp
/usr/share/acl2-6.3/books/xdoc/autolink.lisp
/usr/share/acl2-6.3/books/xdoc/base.acl2
/usr/share/acl2-6.3/books/xdoc/base.lisp
/usr/share/acl2-6.3/books/xdoc/book-thms-example.lisp
/usr/share/acl2-6.3/books/xdoc/book-thms.acl2
/usr/share/acl2-6.3/books/xdoc/book-thms.lisp
/usr/share/acl2-6.3/books/xdoc/cert.acl2
/usr/share/acl2-6.3/books/xdoc/debug.lisp
/usr/share/acl2-6.3/books/xdoc/defsection-tests.lisp
/usr/share/acl2-6.3/books/xdoc/defxdoc-raw.lisp
/usr/share/acl2-6.3/books/xdoc/display.lisp
/usr/share/acl2-6.3/books/xdoc/fmt-to-str.lisp
/usr/share/acl2-6.3/books/xdoc/import-acl2doc.lisp
/usr/share/acl2-6.3/books/xdoc/importance.lisp
/usr/share/acl2-6.3/books/xdoc/names.lisp
/usr/share/acl2-6.3/books/xdoc/parse-xml.lisp
/usr/share/acl2-6.3/books/xdoc/portcullis.acl2
/usr/share/acl2-6.3/books/xdoc/portcullis.lisp
/usr/share/acl2-6.3/books/xdoc/prepare-topic.lisp
/usr/share/acl2-6.3/books/xdoc/preprocess.lisp
/usr/share/acl2-6.3/books/xdoc/save-classic.lisp
/usr/share/acl2-6.3/books/xdoc/save-fancy.lisp
/usr/share/acl2-6.3/books/xdoc/sort.lisp
/usr/share/acl2-6.3/books/xdoc/spellcheck.lisp
/usr/share/acl2-6.3/books/xdoc/top.acl2
/usr/share/acl2-6.3/books/xdoc/top.lisp
/usr/share/acl2-6.3/books/xdoc/topics.lisp
/usr/share/acl2-6.3/books/xdoc/word-wrap.lisp
/usr/share/acl2-6.3/books/xdoc/write-acl2-xdoc.lisp