Graeber, David. Fragments of an anarchist anthropology. 2nd pr.. Chicago: Prickly Paradigm Press, 2004, p. 24. ISBN 978-0-9728196-4-0. The examples given (self-governing communities, radical labour unions, popular militias) reflect the Idea/Economics/Physical taxonomy
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Buber, Martin. Paths in Utopia. Reprint. Syracuse, NY: Syracuse University Press, 1996, p. 104. ISBN 9780815604211.