1. A. Carrington and A. D. McLachlan, Introduction to Magnetic Resonance, Harper & Row, New York (1967).
2. J. E. Wertz and J. R. Bolton, Electron Spin Resonance, Elementary Theory and Practical Applications, McGraw-Hill, New York (1972).
3. N. M. Atherton, Electron Spin Resonance, Theory and Applications, John Wiley & Sons, New York (1973).
4. F. Gerson, High Resolution E.S.R. Spectroscopy, Verlag Chemie, Weinheim (1970).
5. F. Bruin, F. W. Heineken, M. Bruin, and A. Zahlan, ESR spectrum of the 4,4′-dipyridyl radical, J. Chem. Phys. 36, 2783–2785 (1962).