1. . Medicinal Plants of South Africa. Briza: Pretoria, ZA, 1997; 122.
2. . The Medicinal and Poisonous Plants of Southern and Eastern Africa. E & S. Livingstone: Edinburgh, 1962; 228, 250.
3. . In Aromatic Plants: Basic and Applied Aspects, (eds). Martinus Nijhoff: The Hague, The Netherlands, 1982; 255- 263.
4. . Paper No. B15, 31st International Symposium on Essential Oils 2000, Hamburg, Germany.