APA (7 वां संस्करण) प्रशस्ति पत्र

Orr, D. W. (2011). Hope is an imperative: The essential David Orr. Island Press.

शिकागो शैली (17वां संस्करण) प्रशस्ति पत्र

Orr, David W. Hope Is an Imperative: The Essential David Orr. Washington, DC: Island Press, 2011.

एमएलए (9वां संस्करण) प्रशस्ति पत्र

Orr, David W. Hope Is an Imperative: The Essential David Orr. Island Press, 2011.