1. and , in: Paramagnetic Resonance, Vol. 2, Ed. Academic Press, New York 1963 (p. 620).
2. in: Electron Paramagnetic Resonance, Ed. Plenum Press, New York 1972 (p. 1).
3. , , and , Proc. XX. Congr. Ampere, Tallin 1978, Springer-Verlag, Berlin/Heidelberg/New York 1979 (p. 272).