Spengler, J. J. (1972). Population economics: Selected essays of Joseph John Spengler. Duke University Press.
Lua i Stíl Chicago (17ú heag.)Spengler, Joseph John. Population Economics: Selected Essays of Joseph John Spengler. Durham, North Carolina: Duke University Press, 1972.
Lua MLA (9ú heag.)Spengler, Joseph John. Population Economics: Selected Essays of Joseph John Spengler. Duke University Press, 1972.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.