1. J. B. Harborne, Comparative Biochemistry of Flavonoids, Academic Press, New York (1967).
2. R. Semrau, Über die Flavone in der Familie des Labiateen, Dissertation, Munich (1958).
3. S. Hattori and K. Hayashi, Chem. Ber.,66, 279 (1933).
4. K. Shibata, S. Iwata, and J. Nakamura, Acta Phytochim.,1, 106 (1923).
5. C. A. Marsh, Biochem. J.,59, 58 (1955).