@misc{indiciaedc05eafad39d,
  title = {Extended coupled-cluster method. II. Excited states and generalized random-phase approximation.},
  author = {JS Arponen and RF Bishop and E Pajanne},
  year = {1987},
  doi = {10.1103/physreva.36.2539},
  url = {https://pubmed.ncbi.nlm.nih.gov/9899158/},
  note = {Source identifier: 9899158}
}