/usr/share/acl2-6.3/books/data-structures/ is in acl2-books-certs 6.3-5.
This file is owned by root:root, with mode 0o755.
..
/usr/share/acl2-6.3/books/data-structures/alist-defthms.cert
/usr/share/acl2-6.3/books/data-structures/alist-defuns.cert
/usr/share/acl2-6.3/books/data-structures/alist-theory.cert
/usr/share/acl2-6.3/books/data-structures/array1.cert
/usr/share/acl2-6.3/books/data-structures/defalist.cert
/usr/share/acl2-6.3/books/data-structures/deflist.cert
/usr/share/acl2-6.3/books/data-structures/doc-section.cert
/usr/share/acl2-6.3/books/data-structures/list-defthms.cert
/usr/share/acl2-6.3/books/data-structures/list-defuns.cert
/usr/share/acl2-6.3/books/data-structures/list-theory.cert
/usr/share/acl2-6.3/books/data-structures/memories/
/usr/share/acl2-6.3/books/data-structures/memories/log2.cert
/usr/share/acl2-6.3/books/data-structures/memories/memory-impl.cert
/usr/share/acl2-6.3/books/data-structures/memories/memory.cert
/usr/share/acl2-6.3/books/data-structures/memories/memtree.cert
/usr/share/acl2-6.3/books/data-structures/memories/private.cert
/usr/share/acl2-6.3/books/data-structures/no-duplicates.cert
/usr/share/acl2-6.3/books/data-structures/number-list-defthms.cert
/usr/share/acl2-6.3/books/data-structures/number-list-defuns.cert
/usr/share/acl2-6.3/books/data-structures/number-list-theory.cert
/usr/share/acl2-6.3/books/data-structures/set-defthms.cert
/usr/share/acl2-6.3/books/data-structures/set-defuns.cert
/usr/share/acl2-6.3/books/data-structures/set-theory.cert
/usr/share/acl2-6.3/books/data-structures/structures.cert
/usr/share/acl2-6.3/books/data-structures/utilities.cert