Spengler, J. J. (1975). Zero population growth: Implications. Carolina Population Center, University of North Carolina at Chapel Hill.
Lua i Stíl Chicago (17ú heag.)Spengler, Joseph John. Zero Population Growth: Implications. Chapel Hill: Carolina Population Center, University of North Carolina at Chapel Hill, 1975.
Lua MLA (9ú heag.)Spengler, Joseph John. Zero Population Growth: Implications. Carolina Population Center, University of North Carolina at Chapel Hill, 1975.
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