Sage Publications, Lond
Buku Teks
Henslin, James M., author
Pearson , 2010
Buku Teks
Stewart, Elbert W.
Tata McGraw-Hill , 1976
Buku Teks
Schrag, Clarence C., author
Harper & Row, 1963
Buku Teks
Zanden, James W. Vander, author
John Wiley & Sons, 1979
Buku Teks