/usr/share/acl2-7.1/books/ordinals/ is in acl2-books 7.1-1.
This file is owned by root:root, with mode 0o755.
..
/usr/share/acl2-7.1/books/ordinals/e0-ordinal.o
/usr/share/acl2-7.1/books/ordinals/lexicographic-book.o
/usr/share/acl2-7.1/books/ordinals/lexicographic-ordering-without-arithmetic.o
/usr/share/acl2-7.1/books/ordinals/lexicographic-ordering.o
/usr/share/acl2-7.1/books/ordinals/limits.o
/usr/share/acl2-7.1/books/ordinals/ordinal-addition.o
/usr/share/acl2-7.1/books/ordinals/ordinal-basic-thms.o
/usr/share/acl2-7.1/books/ordinals/ordinal-counter-examples.o
/usr/share/acl2-7.1/books/ordinals/ordinal-definitions.o
/usr/share/acl2-7.1/books/ordinals/ordinal-exponentiation.o
/usr/share/acl2-7.1/books/ordinals/ordinal-isomorphism.o
/usr/share/acl2-7.1/books/ordinals/ordinal-multiplication.o
/usr/share/acl2-7.1/books/ordinals/ordinal-total-order.o
/usr/share/acl2-7.1/books/ordinals/ordinals-without-arithmetic.o
/usr/share/acl2-7.1/books/ordinals/ordinals.o
/usr/share/acl2-7.1/books/ordinals/proof-of-well-foundedness.o
/usr/share/acl2-7.1/books/ordinals/top-with-meta.o