Orr, D. W. (2011). Hope is an imperative: The essential David Orr. Island Press.
芝加哥风格引文Orr, David W. Hope Is an Imperative: The Essential David Orr. Washington, DC: Island Press, 2011.
MLA引文Orr, David W. Hope Is an Imperative: The Essential David Orr. Island Press, 2011.
警告：这些引文格式不一定是100％准确.