@misc{indiciaef229f645016b,
  title = {Perturbation theory without unperturbed solutions.},
  author = {RF Bishop and MF Flynn and M Znojil},
  year = {1989},
  doi = {10.1103/physreva.39.5336},
  url = {https://pubmed.ncbi.nlm.nih.gov/9901098/},
  note = {Source identifier: 9901098}
}