TY  - RPRT
TI  - Useful extremum principle for the variational calculation of matrix elements
AU  - Gerjuoy, E.
AU  - Rau, A. R. P.
AU  - Rosenberg, L.
AU  - Spruch, L.
PY  - 1974
UR  - https://ntrs.nasa.gov/citations/19740040954
ID  - 19740040954
ER  -