1. V. I. Minkin, L. P. Olekhnovich, and Yu. A. Zhdanov, in: Molecular Design of Tautomeric Systems [in Russian], Izd. Rostovsk. Univ., Rostov-on-Don (1977), pp. 4–20.
2. K. C. Joshi and V. N. Pathak, Coord. Chem. Rev., 22, 37–122 (1977).
3. L. N. Ferguson, The Modern Structural Theory of Organic Chemistry, Prentice-Hall Inc., Englewood Cliffs, New York (1964), pp. 368–379.
4. E. S. Gould, Mechanism and Structure in Organic Chemistry, Holt, Reinhart and Winston Inc., New York (1959), pp. 376–384.
5. G. S. Hammond, in: Steric Effects in Organic Chemistry, M. S. Neuman (ed.), John Wiley and Sons, Inc., London (1956), pp. 445–454.