1. Willis, J. C., “A Dictionary of the Flowering Plants and Ferns,” 7th Edition, Cambridge University Press, Cambridge, 1966, p. 199.
2. Taylor, N., Editor, “Taylor's Encyclopedia of Gardening”, 3rd Edition, Houghton Mifflin Co., Boston, 1957, p. 169.
3. Miller, R. W., F. R. Earle and I. A. Wolff, JAOCS42, 817–821 (1965).
4. Litchfield, C., R. D. Harlow and R. Reiser, Ibid.42, 849–857 (1965).
5. Fioriti, J. A., and R. J. Sims, J. Chromatog.32, 761–763 (1968).