DeLamater, John D.
Colorado Westview Press, 2014
Buku Teks
Pines, Ayala
McGraw-Hill, 1993
Buku Teks
Baron, Robert A.
Heights Allyn and Bacon , 1991
Buku Teks
Taylor, Shelley E.
Prentice-Hall, 1997
Buku Teks
Baron, Robert A.
Allyn and Bacon , 1997
Buku Teks