• David Graeber, Toward an Anthropological Theory of Value, 2001
• David Graeber, Debt: The First 5,000 Years, 2011
• Eric Raymond, "Homesteading the Noosphere", 1998-2000

Credits

Picture of a Kula ring gift item, Brocken Inaglory, CC BY-SA 3.0, via Wikimedia Commons