reserve i for Nat,
  j for Element of NAT,
  X,Y,x,y,z for set;

theorem Th34:
  for x being variable holds <*x*> is quasi-loci iff vars x = {}
proof
  let x be variable;
A1: <*x*> = (<*>Vars)^<*x*> by FINSEQ_1:34;
A2: rng {} = {};
  vars x c= {} implies vars x = {};
  hence thesis by A1,A2,Th29,Th31;
end;
