1. G. Herzberg: Molecular Spectra and Molecular Structure; I. Spectra of Diatomic Molecules(Van Nostrand, Princeton, NJ 1950 )
2. G. Herzberg: Molecular Spectra and Molecular Structure; II. Infrared and Raman Sepctra of Polyatomic Molecules(Van Nostrand, Princeton, NJ 1945 )
3. G. Herzberg: Molecular Spectra and Molecular Structure; III. Electronic Spectra and Electronic Structure of Polyatomic Molecules(Van Nostrand, Princeton, NJ 1966 )
4. C.H. Townes, A.L. Schawlow Microwave Spectroscopy( McGraw-Hill, New York 1955 )
5. Z.G. Wang, Y.C. Wang, G.P. Morgan, A.L. Schawlow: Opt. Commun. 48, 398 (1984)