Sawkins, F. J. (1978). The evolving earth. Macmillan.
Lua i Stíl Chicago (17ú heag.)Sawkins, Frederick J. The Evolving Earth. Macmillan, 1978.
Lua MLA (9ú heag.)Sawkins, Frederick J. The Evolving Earth. Macmillan, 1978.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.