reserve x,y,z for object, X,Y for set,
  i,k,n for Nat,
  p,q,r,s for FinSequence,
  w for FinSequence of NAT,
  f for Function;

theorem
  ^elementary_tree 0 = elementary_tree 1
proof
  set T = elementary_tree 0;
  thus ^T = tree(1 |-> T) by FINSEQ_2:59
    .= elementary_tree 1 by Th54;
end;
