SEARCH Articles Figures Tables Degenerate perturbation theory effective Hamiltonian calculations Hamiltonian second-order perturbation theory Hamiltonian theory Moller-Plesset perturbation theory zero-order Hamiltonian Perturbation Hamiltonian Perturbation Theory Based on Quasi-Relativistic Hamiltonians Perturbation Theory Energies from the Coupled Cluster Hamiltonian Perturbation theory Hamiltonian systems Perturbation theory reactions, Hamiltonian equations Perturbation theory zeroth order Hamiltonian Perturbed Hamiltonian Some Applications of Second-order Many-body Perturbation Theory with a Moller-Plesset Reference Hamiltonian