Backler, A. L., & Lazarus, S. (1986). World geography. McDougal, Littell.
Lua i Stíl Chicago (17ú heag.)Backler, Alan L., agus Stuart Lazarus. World Geography. Evanston: McDougal, Littell, 1986.
Lua MLA (8ú heag.)Backler, Alan L., agus Stuart Lazarus. World Geography. McDougal, Littell, 1986.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.