Bronitsky, Gordon. Anon.1977. An ecological model of trade: Prehistoric economic change in the northern Rio Grande region of New Mexico. Anthropology. Anthropology. University of Arizona. http://ezproxy.library.arizona.edu/login?url=http://proquest.umi.com/pqdweb?did=759276391&sid=29&Fmt=1&clientId=43922&RQT=309&VName=PQD.