RICHARDS, R. (1991). An Early Start To The Environment. Simon & Schuster.
Lua i Stíl Chicago (17ú heag.)RICHARDS, Roy. An Early Start To The Environment. Simon & Schuster, 1991.
Lua MLA (8ú heag.)RICHARDS, Roy. An Early Start To The Environment. Simon & Schuster, 1991.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.