TY  - RPRT
TI  - Perturbation theory without unperturbed solutions.
AU  - RF Bishop
AU  - MF Flynn
AU  - M Znojil
PY  - 1989
DO  - 10.1103/physreva.39.5336
UR  - https://pubmed.ncbi.nlm.nih.gov/9901098/
ID  - 9901098
ER  -