QDVPT: Quasi-Degenerate Variational Perturbation Theory

What does QDVPT mean? The above is one of QDVPT meanings. It may have other definitions. Please refer to the end of this passage.

QDVPT: Quasi-Degenerate Variational Perturbation Theory

Definition in English: Quasi-Degenerate Variational Perturbation Theory