Behrens, Clifford A. 1989. ?The Scientific Basis For Shipibo Soil Classification And Land Use: Changes In Soil-Plant Associations With Cash Cropping?. American Anthropologist 91 (1): 83-100. doi:10.1525/aa.1989.91.1.02a00050. https://anthrosource.onlinelibrary.wiley.com/doi/abs/10.1525/aa.1989.91.1.02a00050.

Behrens, Clifford A. 1986. ?Relationships Between Shipibo And Western Soil Classification: Changes In Land Use Patterns With Cash Cropping?. In Paper Presented At 85Th Annual Meeting Of The American Anthropological Association, 5 December 1986, Philidelphia.