TY  - GEN
TI  - Qualitative intruder-state problems in effective Hamiltonian theory and their solution through intermediate Hamiltonians
SN  - 0556-2791
PY  - 1987///
PB  - Physical review. A, General physics
N1  - Publication Type: Journal Article
UR  - https://doi.org/10.1103/physreva.35.4930
ER  -