Blum, Milton L.
Harper & Brothers , 1956
Buku Teks
DeLamater, John D.
Colorado Westview Press, 2014
Buku Teks SO
Kwang-Kuo, Hwang
Springer, 2012
eBooks
Taylor, Shelley E.
Prentice-Hall, 1997
Buku Teks SO
Baron, Robert A.
Allyn and Bacon , 1997
Buku Teks SO