Even though non-exhaustive, we report in List 1 some formulas found in the literature to estimate correlated energies in the basis set limit, when extrapolated according to X = 2(D), 3(T), 4(Q), 5, .. ),( )) are all based on empirical interpolations of the total energy, with the difference that Truhlar suggested different powers for the convergence of the HF and MP2c energies. All expressions contain three parameters and therefore require at least three points for extrapolation. However, in the case of the expressions from Truhlar, α = 3.4 and β = 2.2 were found to provide a minimal RMSD with respect to MP2-R12 energies of small systems, so that these can also be used for two-point extrapolations (e.g., DT, TQ, Q5). In some cases, it has been argued that the CBS values calculated directly from relative rather than total energies are more accurate , but no clear explanation or justification was provided to support that claim .