1. Andrews, Anthony P., 1983, Maya Salt Production and Trade, The University of Arizona Press, Tucson.
2. Appel, Jill, n.d., Obsidian Production and Distribution in Periods IIIA through V, Unpublished Manuscript, Department of Sociology and Anthropology, Purdue University, West Lafayette.
3. Arnold, Hugh M., 1940, The Greek City from Alexander to Justinian, Clarendon Press, Oxford.
4. Ball, Joseph W., 1983, Teotihuacan, the Maya, and Ceramic Interchange: A Contextual Perspective, in: Highland-Lowland Interaction in Mesoamerka: Interdisciplinary Approaches (Arthur G. Miller, ed.), Dumbarton Oaks, Washington, D.C., pp. 125–146.
5. Bedoian, William H., 1973, Oro y Maiz: The Economic Structure of the Mexica Empire and its Effects on Social Stratification and Political Power, Unpublished MA Thesis, Department of Anthropology, The Pennsylvania State University, University Park.