Orr, D. W. (2011). Hope is an imperative: The essential David Orr. Island Press.
Chicago-viite (17. p.)Orr, David W. Hope Is an Imperative: The Essential David Orr. Washington, DC: Island Press, 2011.
MLA-viite (9. p.)Orr, David W. Hope Is an Imperative: The Essential David Orr. Island Press, 2011.
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