The following books should certify in v2-7, v2-8, etc. The definitions in n2n.lisp test
the version since there are a couple of functions whose definitions change from v2-7 to
v2-8 (see n2n.lisp for details).

fair1.lisp    -- a "book" demonstrating the logical equivalence between our fair
                 env. assumptions and a straightforward statement of (fair-selection)
example1.lisp -- a simple example application of the straightforward fair selector
                 defined in fair1.lisp.
                 -- the fair selector in fair2.lisp is a better book to use than
                    fair1.lisp because it does not require the (fair-selection)
                    constant predicate as an hypothesis to liveness and other theorems.
simple.lisp   -- a simple fair selector over bounded naturals
                 -- only provided for exposition, this is completely subsumed
                    by fair2.lisp
n2n.lisp      -- an invertible function from the "nice" or "good" ACL2 objects
                 to natural numbers
fair2.lisp    -- an unconditional fair selection environment for "nice" ACL2 objects
example2.lisp -- a simple example application of the unconditional fair selector in
                 fair2.lisp
example3.lisp -- a more complex application of the unconditional fair selector in 
                 fair2.lisp
cfair.lisp    -- a conditional fair selector for "nice" ACL2 objects
