Finally, Varandas investigated the universality of the B parameter in Helgaker (29), and found that Eq. Varandas3-fit (31) minimizes the difference with a set of CCSD(T)/MP2 energies of small molecules and different basis sets . However, the match was better if considering a fourth order term with the general form of Varandas34 (30), or by exploiting an empirical interdependence between the parameters that leads to Eq. Var.34-fit (32) which has the advantage of requiring only two points for extrapolation.