Slocum, Stephanie A., author
Syracuse University Press, 2003
Buku Teks
New York: W.W.Norton & Company, 1988,
Buku Referensi
Sethi, S. Prakash, author
Prentice-Hall, 1974
Buku Teks
Douglas, William O., author
Princeton University Press, 1960
Buku Teks
Douglas, William O., author
Princeton University Press , 1960
Buku Teks SO