1. Bothorel, P. and Lussan, C.: 1968. C.R. Acad. Sci. Ser. D. Paris 266. pp. 1118–1120.
2. Singer, S.S. and Nicolson, G.L.: 1972. Science, N.Y. 175, pp. 720–731.
3. Rozantsev, E.G.: 1970, Free Nitroxyl Radicals, Plenum Press, New-York.
4. A very complete view on theory and applications of spin labeling is given in: Spin Labeling
5. Berliner, L.J. ed., Academic Press, New-York, tome I 1976, tome II 1979.