1. Streitwieser Jr A, Heathcock CH (1976) Introduction to organic chemistry. Macmillan, New York
2. Ternay AL (1979) Contemporary organic chemistry. Saunders, Philadelphia
3. Wheland GW (1953) The theory of resonance and its application to organic chemistry. Wiley, New York
4. Pauling L (1958) The nature of chemical bond, 2nd edn, 12th printing. Wiley, New York
5. Coulson CA (1961) Valence, 2nd edn, Oxford University Press