Lua APA (7ú heag.)

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

Lua i Stíl Chicago (17ú heag.)

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

Lua MLA (9ú heag.)

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

Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.