1. B. O. Roos.Chem. Phys. Letters, 15: 153, 1972.
2. B. O. Roos and P. E. M. Siegbahn. The direct configuration interaction method. In H.F. Schaefer III, editor, Methods of Electronic Structure Theory, page 189. Plenum, New York, 1994.
3. I. Shavitt. In H. F. Schaefer III, editor, Modern Theoretical Chemistry. Plenum, New York, 1977.
4. S. R. Langhoff and E. R. Davidson.Int. J. Quantum Chem., 8: 61, 1974.
5. W. Butscher, S. Shih, R. J. Buenker, and S. D. Peyerimhoff.Chem. Phys. Letters, 52: 457, 1977.