/usr/share/acl2-7.1/books/centaur/bitops/ is in acl2-books 7.1-1.
This file is owned by root:root, with mode 0o755.
..
/usr/share/acl2-7.1/books/centaur/bitops/ash-bounds.o
/usr/share/acl2-7.1/books/centaur/bitops/congruences.o
/usr/share/acl2-7.1/books/centaur/bitops/contrib/
/usr/share/acl2-7.1/books/centaur/bitops/contrib/ash-of-a-constant.o
/usr/share/acl2-7.1/books/centaur/bitops/defaults.o
/usr/share/acl2-7.1/books/centaur/bitops/equal-by-logbitp.o
/usr/share/acl2-7.1/books/centaur/bitops/extra-defs.o
/usr/share/acl2-7.1/books/centaur/bitops/fast-logext.o
/usr/share/acl2-7.1/books/centaur/bitops/fast-logrev.o
/usr/share/acl2-7.1/books/centaur/bitops/fast-rotate.o
/usr/share/acl2-7.1/books/centaur/bitops/ihs-extensions.o
/usr/share/acl2-7.1/books/centaur/bitops/ihsext-basics.o
/usr/share/acl2-7.1/books/centaur/bitops/install-bit.o
/usr/share/acl2-7.1/books/centaur/bitops/integer-length.o
/usr/share/acl2-7.1/books/centaur/bitops/logbitp-bounds.o
/usr/share/acl2-7.1/books/centaur/bitops/logbitp-mismatch.o
/usr/share/acl2-7.1/books/centaur/bitops/merge.o
/usr/share/acl2-7.1/books/centaur/bitops/part-install.o
/usr/share/acl2-7.1/books/centaur/bitops/part-select.o
/usr/share/acl2-7.1/books/centaur/bitops/portcullis.o
/usr/share/acl2-7.1/books/centaur/bitops/rotate.o
/usr/share/acl2-7.1/books/centaur/bitops/saturate.o
/usr/share/acl2-7.1/books/centaur/bitops/signed-byte-p.o
/usr/share/acl2-7.1/books/centaur/bitops/top.o