RAVEN, P. H. (1993). Environment. Saunders College Publishing.
Lua i Stíl Chicago (17ú heag.)RAVEN, Peter H. Environment. Saunders College Publishing, 1993.
Lua MLA (8ú heag.)RAVEN, Peter H. Environment. Saunders College Publishing, 1993.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.