An excellent performance of the SF methods in calculations of singlet-triplet gaps in benzynes and similar aromatic di-and tri-radicals has been illustrated in several benchmark studies . An important prerequisite for accuracy is using not too spin-contaminated reference. In the case of large spin-contamination of the UHF reference, ROHF orbitals, orbitals optimized for a correlated ansatz (i.e., approximate Brueckner's orbitals ), such as OO-CCD or OO-MP2 , or even Kohn-Sham DFT orbitals can be used. As shown below, the spin-contamination of the reference state also affects the performance of the OSFNO approximation.