1. Callen, E. O. 1967. Analysis of the Tehuacan coprolites.In D. S. Byers, ed. The Prehistory of the Tehuacan Valley. Vol. 1: Environment and Subsistence, pp. 261–289. Univ. Texas Press, Austin.
2. Coons, M. P. 1970. The relationship of Ecuadorianquinoa de CastillaandAmaranthus caudatusL. Abstr. Proc. Indiana Acad. Sci. 80: 413.
3. —. 1975. The genusAmaranthusin Ecuador. Ph.D. diss., Indiana Univ. Univ. Microfilms, Ann Arbor, MI.
4. ---. In press. The status ofAmaranthus hybridusL. in South America. Ciencia y Naturaleza. Covas, G. 1950. Un hibrido interespecifico natural en “Amaranthus.” Revista Argent. Agron. 17: 257–260.
5. Grant, V. 1971. Plant Speciation. Columbia Univ. Press, New York.