1. McGrath, J.W.; Silvidi, A.A.:J Chem Phys 36(1962),1496
2. Nakamura, S.; Enokiya, H.:J Phys Soc Jpn 18(1963),183
3. Graybeal, J.D.; McKown, R.J.:J Phys Chem 73(1969),3156
4. Volkov, A.F.; Smirnov, N.I.:Dokl Akad Nauk SSSR 211(1973),1377
5. Volkov, A.F.:J Magn Reson 11(1973),73