/usr/share/acl2-6.3/books/symbolic/ is in acl2-books-certs 6.3-5.
This file is owned by root:root, with mode 0o755.
..
/usr/share/acl2-6.3/books/symbolic/generic/
/usr/share/acl2-6.3/books/symbolic/generic/assertions.cert
/usr/share/acl2-6.3/books/symbolic/generic/defsimulate.cert
/usr/share/acl2-6.3/books/symbolic/generic/factorial-jvm-correct.cert
/usr/share/acl2-6.3/books/symbolic/generic/measures.cert
/usr/share/acl2-6.3/books/symbolic/generic/partial-correctness.cert
/usr/share/acl2-6.3/books/symbolic/generic/tiny-fib-correct.cert
/usr/share/acl2-6.3/books/symbolic/generic/total-correctness.cert
/usr/share/acl2-6.3/books/symbolic/m5/
/usr/share/acl2-6.3/books/symbolic/m5/demo.cert
/usr/share/acl2-6.3/books/symbolic/m5/utilities.cert
/usr/share/acl2-6.3/books/symbolic/tiny-fib/
/usr/share/acl2-6.3/books/symbolic/tiny-fib/defstobj+.cert
/usr/share/acl2-6.3/books/symbolic/tiny-fib/fib-def.cert
/usr/share/acl2-6.3/books/symbolic/tiny-fib/tiny-rewrites.cert
/usr/share/acl2-6.3/books/symbolic/tiny-fib/tiny.cert
/usr/share/acl2-6.3/books/symbolic/tiny-triangle/
/usr/share/acl2-6.3/books/symbolic/tiny-triangle/tiny-triangle-correct.cert
/usr/share/acl2-6.3/books/symbolic/tiny-triangle/triangle-def.cert