Nadia Johnson Penn State No description specified. 1-4 (4 Records) Documents Altica and the Role of Middlemen in Formative Obsidian Exchange (2017) Erosion and Agricultural Resilience in the Formative Teotihuacan Valley (2019) Obsidian Exchange and Use in Early Formative Chalcatzingo (2018) Wild Resource use in Early Colonial New Spain (2016)