actualize
set-union
with
gref
by morphism
:set → refset;
:elem → ref;
∅ → ∅;
++ → ++;
# → #;
{ } → { };
∪ → ∪;
∩ → ∩;
\ → \;
-- → --;
∈ → ∈;
⊆ → ⊆;
s → rs;
s0 → rs0;
s1 → rs1;
s2 → rs2;
a → r;
b → r0;
c → r1
end actualize