/usr/share/acl2-6.3/books/textbook/chap11/ is in acl2-books-source 6.3-5.
This file is owned by root:root, with mode 0o755.
..
/usr/share/acl2-6.3/books/textbook/chap11/compress.lisp
/usr/share/acl2-6.3/books/textbook/chap11/encap.lisp
/usr/share/acl2-6.3/books/textbook/chap11/finite-sets.lisp
/usr/share/acl2-6.3/books/textbook/chap11/how-many-soln1.lisp
/usr/share/acl2-6.3/books/textbook/chap11/how-many-soln2.lisp
/usr/share/acl2-6.3/books/textbook/chap11/mergesort.lisp
/usr/share/acl2-6.3/books/textbook/chap11/perm-append.lisp
/usr/share/acl2-6.3/books/textbook/chap11/perm.lisp
/usr/share/acl2-6.3/books/textbook/chap11/qsort.lisp
/usr/share/acl2-6.3/books/textbook/chap11/starters.lisp
/usr/share/acl2-6.3/books/textbook/chap11/summations-book.lisp
/usr/share/acl2-6.3/books/textbook/chap11/summations.lisp
/usr/share/acl2-6.3/books/textbook/chap11/tautology.lisp
/usr/share/acl2-6.3/books/textbook/chap11/xtr.lisp
/usr/share/acl2-6.3/books/textbook/chap11/xtr2.lisp