SEARCH Articles Figures Tables A Computer-Algebraic Approach to the Derivation of Feynman-Goldstone Perturbation Expansions for Open-Shell Atoms and Molecules A variation-perturbation approach First-principles perturbative approach Fragmentation approach perturbation method Independent systems perturbation approach Intermolecular interaction energy perturbation-theory approach Many-body perturbation approach Many-electron correlation problem perturbative approaches Nonadditivity perturbational approach Perturbation approach Perturbation theory - slightly different approach Perturbation theory approach Perturbational Approaches to Spin-Orbit Coupling Perturbational Molecular Orbital (PMO) Approach Perturbational molecular orbital approach Perturbative approach Perturbative approach Perturbed-function approach Potential energy surface perturbation approach Regular Perturbation Approaches Second-order many-body perturbation approaches The perturbation approach Thermodynamic cycle-perturbation approach Variation-perturbation approach Variation-perturbation approach many-electron theory