1. Balasubramanian, K.: Theoret. Chim. Acta (Berl.) 65, 49 (1984)
2. For a description of this method, see [1]
3. Buschen, J.: Mémoire de Licence, Université Libre de Bruxelles (1974)
4. Brocas, J., Fastenakel, D., Hicquebrand, J., Willem, R.: Bull. Soc. Chim. Belges 82, 629 (1973)
5. Randi?, M., Katovi?, V.: Int. Journ. Quantum. Chem. XV, 683 (1979)