1. H.M. McConnell and D.B. Chesnut, J. Chem. Phys. 28, 107, (1958) and references therein.
2. D.J.E. Ingram, Free Radicals as Studied by Electron Spin Resonance, Academic Press, New York and London (1958); S.A. Al’tshuler and B.M. Kozyrev, Electron Paramagnetic Resonance, Academic Press, New York (1964), Chapter VII.
3. S.A. Al’tshuler and B.M. Kozyrev, Electron Paramagnetic Resonance, Academic Press, New York (1964), Chapter VII.
4. H.J. Gerristen, R. Okkes, H.M. Gisman and J. Van den Handel, Physica 20, 13 (1954).
5. A.M. Prokhorov and V.B. Fedorov, Soviet Phys.—JETP 16, 1489 (1963).