/usr/share/acl2-6.3/books/demos/ is in acl2-books-source 6.3-5.
This file is owned by root:root, with mode 0o755.
..
/usr/share/acl2-6.3/books/demos/constants-that-require-modifying-state.lisp
/usr/share/acl2-6.3/books/demos/list-theory.lisp
/usr/share/acl2-6.3/books/demos/modeling/
/usr/share/acl2-6.3/books/demos/modeling/cert.acl2
/usr/share/acl2-6.3/books/demos/modeling/memories.lisp
/usr/share/acl2-6.3/books/demos/modeling/nested-stobj-toy-isa.acl2
/usr/share/acl2-6.3/books/demos/modeling/nested-stobj-toy-isa.lisp
/usr/share/acl2-6.3/books/demos/modeling/network-state-basic.lisp
/usr/share/acl2-6.3/books/demos/modeling/network-state.lisp
/usr/share/acl2-6.3/books/demos/modeling/nondeterminism.lisp
/usr/share/acl2-6.3/books/demos/split-types-examples.lisp