The books in this directory should be certified with ACL2 v2.5.  They
are:

1.  total-order: this is the book described in section 2.1 of the
    paper.

2.  total-order-easy-direction: this is the book refered to at the end
    of section 2.1.

3.  soundness: this is the book refered to in section 2.2.

