Cummings, Milton C.
Harcourt Brace Jovanovich, 1981
Buku Teks
Geer, John Gray
Wadsworth and Cengage Learning, 2012
Buku Teks
by John G. Geer [and others]
Wadsworth and Cengage Learning, 2012
Buku Teks
Dye, Thomas R.
Harcourt Brace College, 2000
Buku Teks
Dye, Thomas R.
Thomson, 2006
Buku Teks