Pirages, D. C., & Ehrlich, P. R. (1974). Ark II: Social response to environmental imperatives. Freeman.
Lua i Stíl Chicago (17ú heag.)Pirages, Dennis C., agus Paul R. Ehrlich. Ark II: Social Response to Environmental Imperatives. San Francisco: Freeman, 1974.
Lua MLA (9ú heag.)Pirages, Dennis C., agus Paul R. Ehrlich. Ark II: Social Response to Environmental Imperatives. Freeman, 1974.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.