To determine the reference method used for the full test set, we compare 5 levels of MP2 to DF-CCSD(T)-F12b/cc-pVDZ-F12 calculations. We have chosen the given coupled-cluster method, as CCSD(T) consistently has been shown to be an excellent reference method and is extensively used in various prominent benchmarks. The explicit correlation approach (-F12) has been shown to approach the basis set limit faster than the conventional approach. In cases where CCSD(T) (O(n 7 )) is not feasible, MP2 (O(n 5 )) is often used as a cheaper alternative wave function-based approach. MP2 has been shown to give very reliable results and should be a highly suitable reference for geometries.