Cummings, Milton C.
Harcourt Brace Jovanovich, 1981
Buku Teks
Ranney, Austin
Harcourt, Brace and Company, 1956
Buku Teks
Geer, John Gray
Wadsworth and Cengage Learning, 2012
Buku Teks
Dye, Thomas R.
Harcourt Brace College, 2000
Buku Teks
Dye, Thomas R.
Thomson, 2006
Buku Teks