theorem Th11:
  S is Sub_atomic implies S`1 is atomic
proof
  assume S is Sub_atomic;
  then consider
  k being Nat, P being (QC-pred_symbol of k,A), ll being
  QC-variable_list of k,A, e being Element of vSUB(A) such that
A1: S = Sub_P(P,ll,e);
  S = [P!ll,e] by A1,Th9;
  then S`1 = P!ll;
  hence thesis;
end;
