1. El Sissi, H. I. &El Sherbeiny, A. E. A. - 1967 -Qual. Plant. Mater. veg., XIV:28.
2. Geissman, T. A. - 1955 - Modern Methods of Plant Analysis, vol. III, p. 476, Berlin, Göttingen, Heidelberg-Springer.
3. Shimizu, M. - 1951 -J. Pharm. Soc. Japan, 71:1329.
4. Bate-Smith, E. C. &Lerner, N. H. - 1954 -Biochem. J., 58:126.
5. Bate-Smith, E. S. &Swain, T. -1953 -Chem. and Ind., 377.