TY  - RPRT
TI  - Nonlinear sum rules: The three-level and the anharmonic-oscillator models.
AU  - S Scandolo
AU  - F Bassani
PY  - 1992
DO  - 10.1103/physrevb.45.13257
UR  - https://pubmed.ncbi.nlm.nih.gov/10001406/
ID  - 10001406
ER  -