[Studies on the components of essential oils. III. Studies of chemical constituents of the essential oil from Rhododendron racemosum Franch. (I) Comparison of the constituents of Vitex negundo L. var. Cannabifolia (Sieb. et Zucc.) Hand-Mazz. (II) and V. Negundo L. var. Heterophylla (Franch.) Rehd. (III) (author's transl)].