T. Thorsteinsson and D. L. Cooper.
Mol. Phys. 93, 663-674 (1998).

Abstract

An implementation of a biorthogonal approach to modern valence bond calculations is presented emphasizing the problems associated with larger numbers of active electrons. A full treatment of up to 20 active electrons seems feasible within this strategy. We propose a restricted-step second-order algorithm which may be of use also for other non-symmetrical optimization problems. Applications to the ground states of methylene and naphthalene are presented. highlighting the difference between a biorthogonal approach and the analogous variational calculations.

Online text

Here (note: full text not available).