1. See, for example, (a) P. Pulay, Direct use of the gradient for investigation molecular energy surfaces, in: “Applications of Electronic Structure”, H. F. Schaefer III, ed., Plenum, New York (1977), p. 153.
2. J. A. Pople, R. Krishnan, H. B. Schlegel, and J. S. Binkley, Derivative studies in Hartree-Fock and Møller-Plesset theories, Int. J. Quantum Chem. Symp. 13: 225 (1979).
3. B. R. Brooks, W. D. Laidig, P. Saxe, J. D. Goddard, Y. Yamaguchi, and H. F. Schaefer III, Analytic gradients from correlated wavefunctions via the two-particle density matrix and the unitary group approach, J. Chem. Phys. 72: 4652 (1980).
4. K. Fukui, S. Kato, and H. Fujimoto, Constituent analysis of the potential gradient along a reaction coordinate. Method and an application to CH4 + T reaction, J. Amer. Chem. Soc. 97: 1 (1975).
5. H. F. Schaefer III, Potential energy surfaces for methylene reactions, Chem. Britain 11: 227 (1975).