1. Alston, R. E.: Chemotaxonomy or biochemical systematics. In: T. Swain (Editor): Comparative phytochemistry, pp. 33–56. Academic Press. London and New York. 1966.
2. Alston, R. E., u. B. L. Turner: Biochemical systematics. Prentice Hall, Inc. Englewood Cliffs, N. J. 1963.
3. Benson, L.: Plant taxonomy. Methods and principles. The Ronald Press Company. New York. 1962.
4. Benson, L.: Plant classification. Second edition. D. C. Heath and Company. Lexington, Massachusetts and Toronto. 1979.
5. Bjeldanes, L. F., u. T. A. Geissman: Sesquiterpene lactones: Constituents of an F1 hybrid Encelia farinosa × Encelia californica. Phytochemistry 10, 1079–1081 (1971).