1. Ramsey, N. F.: Physic. Rev. 91, 303 (1953).
2. Pople, J. A., H. J. Bernstein, and W. G. Schneider: High-resolution Nuclear Magnetic Resonance. New York: McGraw-Hill 1959.
3. Slichter, C. P.: Principles of Magnetic Resonance. New York: Harper and Row 1963.
4. Pauling, L.: J. chem. Physics 1, 280 (1933).
5. Fermi, E.: Z. Physik 60, 320 (1930).