@booklet {7439,
	title = {FRICK, C. and MALHERBE, S.J. 1986. The geology of the Roodeplaat caldera, north-east of Pretoria. Bulletin, Geological Survey of South Africa, 79: 1-44.LOMBAARD, B. 1930. The geology of a centrocline, 18 miles north-east of Pretoria. Transactions and Proc},
	year = {1986},
	note = {FRICK, C. and MALHERBE, S.J. 1986. The geology of the Roodeplaat caldera, north-east of Pretoria. Bulletin, Geological Survey of South Africa, 79: 1-44.LOMBAARD, B. 1930. The geology of a centrocline, 18 miles north-east of Pretoria. Transactions and Proceedings of the Geological Society of South Africa, 32: 151-00-64.SHAND, S.J. 1922. The alkaline rocks of the Franspoort line, Pretoria district. Transactions of the Geological Society of South Africa, 25: 81-100.VERWOERD, W.J. 1967. The carbonatites of South Africa and South West Africa. Geological Survey of South Africa, Handbook, 6: 1-452.VERWOERD, W.J. 1993. Update on carbonatites of South Africa and Namibia. South African Journal of Geology, 96: 75-95.}
}
