1. Davies, G. Chem. Phys. Carbon 13, 1–143 (1977).
2. Burgemeister, E. A. J. Phys. C 13, L963–968 (1980).
3. Dyer, H. B., Raal, E. A., du Preez, I. & Loubser, J. H. N. Phil. Mag. 11, 763–774 (1965).
4. Davies, G. J. Phys. C 9, L537–542 (1976).
5. Sobolev, E. V., Lisoivan, V. I. & Lenskaya, S. V. Soviet Phys. Crystallogr. 12, 665–668 (1968).