Le Roy, Michael K.
Wadsworth and Cengage Learning, 2013
Buku Teks
Craig, James R.
Saunders, 1986
Buku Teks
Le Roy, Michael K.
Wadsworth, 2009
Buku Teks
Johnson, Janet Buttolph, 1950-
CQ Press, 2012
Buku Teks
Good, Carter V.
Appleton Century Crofts, 1954
Buku Teks