SEARCH Articles Figures Tables Brillouin-Wigner perturbation theory single-reference Many-body perturbation theory singles Perturbation expansion, single-reference Perturbation expansion, single-reference function Perturbation theory single-root formulation Single Line Perturbation Experiment Single Perturbation Methods Single reference many-body perturbation Single-reference function perturbation Single-reference many-body perturbation theory Single-reference perturbative methods Single-root formulation of multi-reference Brillouin-Wigner perturbation theory Single-step perturbation