1. D. F. Shriver , P. W.Atkins and C. H.Langford , Inorganic Chemistry , O.U.P. , Oxford , 1990 , p. 68
2. G. Wulfsberg , Inorganic Chemistry , University Science Books , Sausalito, CA , 2000 , p. 31
3. G. Herzberg , Molecular Spectra and Molecular Structure I Spectra of Diatomic Molecules , Van Nostrand Reinhold , NY , 1950 , pp. 501–581
4. K. P. Huber and G.Herzberg , Molecular Spectra and Molecular Structure IV Constants of Diatomic Molecules , Van Nostrand Reinhold , NY , 1979 , pp. 7–689
5. A. F. Wells , Structural Inorganic Chemistry , Oxford University Press , Oxford , 5th edn, 1984