1. Ahrens, L. H.: Variation of refractive index with ionization potential in some isostructural crystals. Mineral. Mag. 31, 929?936 (1958).
2. ?, Cherry, R. D., Erlank, A. J.: Observations on the Th-U relationship in zircons from granitic rocks and from kimberlites. Geochim. Cosmochim. Acta 31, 2379?2387 (1967).
3. Beck, R.: Untersuchungen über einige südafrikanische Diamantenlagerstätten. Z. Deut. Geol. Ges. 59 279?307 (1907).
4. Berg, G. W.: Secondary alteration in eclogites from kimberlite pipes. Am. Mineralogist 53, 1336?1346 (1968).
5. Dawson, J. B.: Basutoland kimberlites. Bull. Geol. Soc. Am. 73, 545?560 (1962).