* 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 `r[x/n]`, that's our `g{x:=n}`.
* Their function `g`, which assigns objects from the domain to pegs, corresponds to our store function, which assigns entities to indexes.
* 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 `r[x/n]`, that's our `g{x:=n}`.
* Their function `g`, which assigns objects from the domain to pegs, corresponds to our store function, which assigns entities to indexes.