S Hirata, X He, M R Hermes, S Y Willow, Second-Order Many-Body Perturbation Theory: An Eternal Frontier, JPCA 118, 655 (2014)
S Grimme, Improved second-order Moller-Plesset perturbation theory by separate scaling of parallel- and antiparallel-spin pair correlation energies, JCP 118, 9095 (2003) – SCS-MP2