Histrionicotoxins: Roentgen-ray analysis of the novel allenic and acetylenic spiroalkaloids isolated from a Colombian frog, Dendrobates histrionicus: Daly, J. W., Karle, I., Myers, C. W., Tokuyama, T., Waters, J. A. and Witkip, B. (National Institute of Arthritis and Metabolic Diseases, NIH, Bethesda, Md.; Naval Research Laboratory, Washington, D.C.; American Museum of Natural History, New York, N.Y.; Osaka City University, Osaka, Japan). Proc. Nat. Acad. Sci. U.S.A.68, 1870, 1971