1. Lucken,E.A.C.: Nuclear quadrupole coupling constants, Chapter 10 and 11. New York: Academic Press 1969
2. Lucken,E.A.C.: In: Katritzky,A.R. (Ed.): Physical methods in heterocyclic chemistry, Vol. 4, Chapter 2. New York: Academic Press 1971
3. Pople,J.A., Beveridge,D.L., Dobosh,P.A.: J. Chem. Phys. 47, 2026 (1969)
4. See e.g.: Maciel,G.E., McIver,J.W.Jr., Ostlund,N.S., Pople,J.A.: J. Am. Chem. Soc. 92, 1, 11, 4497 (1970)
5. Wasylishen,R., Schaefer,T.: Can. J. Chem. 50, 2989 (1972); 51, 961 (1973)