* Where they represent pegs as natural numbers, that corresponds to our representing locations in a store by their indexes in the store.
-* 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.
* Where they say `r[x/n]`, that's our `g{x:=n}`.