Folks, J. Leroy
John Wiley & Sons, 1981
Buku Teks
Lamont, Douglas
Blackwell Publishers, 1996
Buku Referensi
Chang, David W.
Thomson/Delmar Learning, 2006
Buku Teks
Robbins, Robert R.
John Wiley & Sons, 1981
Buku Teks
Nunnally, Jum C.
McGraw-Hill, 1970
Buku Teks