@misc{indiciae3963086be7e7,
  title = {Perturbation theory in multireference spaces.},
  author = {W Duch and GH Diercksen},
  year = {1992},
  doi = {10.1103/physreva.46.95},
  url = {https://pubmed.ncbi.nlm.nih.gov/9907839/},
  note = {Source identifier: 9907839}
}