Lundberg, George Andrew
D. McKay Co, 1964
Buku Teks
Bell, Earl H.
Harper & Row, 1965
Buku Teks
Schrag, Clarence C., author
Harper & Row, 1963
Buku Teks
Zanden, James W. Vander, author
John Wiley & Sons, 1979
Buku Teks
Ogburn, William F., author
Houghton Mifflin, 1946
Buku Teks