Scheaffer, R. L. (1979). Elementary survey sampling. Duxbury Press.
Lua i Stíl Chicago (17ú heag.)Scheaffer, Richard L. Elementary Survey Sampling. Duxbury Press, 1979.
Lua MLA (8ú heag.)Scheaffer, Richard L. Elementary Survey Sampling. Duxbury Press, 1979.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.