1. Hurry, J. B., in The Woad Plant and its Dye, 328 (Oxford Univ. Press, 1930).
2. Sachs, J. H., in Encyclopaedia Britannica, 10, 256 (1963).
3. Dictionary of Organic Compounds, 3, 1845 (Oxford Univ. Press, 1965).
4. Karrer, W., in Konstitution und Vorkommen der organischen Pflanzenstoffe, 1035 (Birkhauser Verlag, Basel, 1958).
5. Robinson, T., in The Organic Constituents of Higher Plants, 292 (Burgess Publishing Co., Minneapolis, Minn., 1963).