Williams, D. (1922). Darwin. Frye & Smith.
Lua i Stíl Chicago (17ú heag.)Williams, Digain. Darwin. San Diego, Calif.: Frye & Smith, 1922.
Lua MLA (8ú heag.)Williams, Digain. Darwin. Frye & Smith, 1922.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.