/usr/share/acl2-7.1/books/nonstd/ is in acl2-books 7.1-1.
This file is owned by root:root, with mode 0o755.
..
/usr/share/acl2-7.1/books/nonstd/fft/
/usr/share/acl2-7.1/books/nonstd/fft/eval-poly.o
/usr/share/acl2-7.1/books/nonstd/fft/fft-omega.o
/usr/share/acl2-7.1/books/nonstd/nsa/
/usr/share/acl2-7.1/books/nonstd/nsa/inner-sums.o
/usr/share/acl2-7.1/books/nonstd/sqrt/
/usr/share/acl2-7.1/books/nonstd/sqrt/iter-sqrt.o
/usr/share/acl2-7.1/books/nonstd/workshops/
/usr/share/acl2-7.1/books/nonstd/workshops/1999/
/usr/share/acl2-7.1/books/nonstd/workshops/1999/calculus/
/usr/share/acl2-7.1/books/nonstd/workshops/1999/calculus/book/
/usr/share/acl2-7.1/books/nonstd/workshops/1999/calculus/book/top-with-meta.o
/usr/share/acl2-7.1/books/nonstd/workshops/1999/calculus/solutions/
/usr/share/acl2-7.1/books/nonstd/workshops/1999/calculus/solutions/mesh-append.o
/usr/share/acl2-7.1/books/nonstd/workshops/1999/calculus/solutions/mesh-make-partition.o
/usr/share/acl2-7.1/books/nonstd/workshops/1999/calculus/solutions/partition-defuns.o
/usr/share/acl2-7.1/books/nonstd/workshops/1999/calculus/solutions/partitionp-make-partition-rec.o
/usr/share/acl2-7.1/books/nonstd/workshops/1999/calculus/solutions/partitionp-make-partition.o
/usr/share/acl2-7.1/books/nonstd/workshops/1999/calculus/solutions/riemann-rcfn-helpers.o
/usr/share/acl2-7.1/books/nonstd/workshops/2011/
/usr/share/acl2-7.1/books/nonstd/workshops/2011/reid-gamboa-differentiator/
/usr/share/acl2-7.1/books/nonstd/workshops/2011/reid-gamboa-differentiator/support/
/usr/share/acl2-7.1/books/nonstd/workshops/2011/reid-gamboa-differentiator/support/composition-helpers.o
/usr/share/acl2-7.1/books/nonstd/workshops/2011/reid-gamboa-differentiator/support/defderivative.o