Spengler, J. J. (1972). Population economics: Selected essays of Joseph John Spengler. Duke University Press.
Chicago-viite (17. p.)Spengler, Joseph John. Population Economics: Selected Essays of Joseph John Spengler. Durham, North Carolina: Duke University Press, 1972.
MLA-viite (9. p.)Spengler, Joseph John. Population Economics: Selected Essays of Joseph John Spengler. Duke University Press, 1972.
Varoitus: Nämä viitteet eivät aina ole täysin luotettavia.