theorem Th28:
  for A being Subset of bound_QC-variables(Al) st A is finite holds
  ex x st not x in A
proof
  let A be Subset of bound_QC-variables(Al);
  A1: not bound_QC-variables(Al) is finite by CALCUL_1:64;
  assume A is finite;
  then not (for b being object holds b in A iff b in bound_QC-variables(Al))
  by A1,TARSKI:2;
  then consider b such that
A2: not b in A and
A3: b in bound_QC-variables(Al);
  reconsider x = b as bound_QC-variable of Al by A3;
  take x;
  thus thesis by A2;
end;
