-* Where they work with sets of blahs, you should generally think in terms of functions from blahs to bools.
-
-* Where they say "reference system," which they use the leter `r` for, that corresponds to what we've been calling "assignments", and use the letter `g` for.
+* Where they say "reference system," which they use the leter `r` for, that corresponds to what we've been calling "assignments", and have been using the letter `g` for.