Keyfitz, N. (1990). World population growth and aging: Demographic trends in the late twentieth century. University of Chicago Press.
Lua i Stíl Chicago (17ú heag.)Keyfitz, Nathan. World Population Growth and Aging: Demographic Trends in the Late Twentieth Century. Chicago: University of Chicago Press, 1990.
Lua MLA (9ú heag.)Keyfitz, Nathan. World Population Growth and Aging: Demographic Trends in the Late Twentieth Century. University of Chicago Press, 1990.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.