United States. Departement of Comerce
Bureau of the Census, 1960
Buku Referensi
Shapiro, Sam
Harvard University Press, 1968
Buku Teks
Schmookler, Jacob
Harvard University Press, 1972
Buku Teks
Bemis, Samuel Flagg, 1891-1973, author
Harcourt, Brace, 1943
Buku Teks
Allard, Patsy Bailey, author
AMA Membership Publications Division, American Management Associations, 1983
Buku Referensi