1. H. Geiger , in The Flavonoids. Advances in Research since 1986, ed. J. B. Harborne, Chapman and Hall, London, 1994, p. 96 and references cited therein.
2. K. C. Palgrave , in Trees of Southern Africa, ed. J. Moll, C. Struik Publishers, Cape Town, 1983, p. 553.
3. B. A. Bohm , in The Flavonoids. Advances in Research since 1986, ed. J. B. Harborne, Chapman and Hall, London, 1988, p. 329.