Westview Press , 1985
Buku Teks
Christian Soe
McGraw-Hill, 2004
Buku Teks
Barringron, Lowell, author
Wadsworth and Cengage Learning, 2013
Buku Teks
Chilcote, Ronald H., author
Routledge, 2000
eBooks
McCormick, John, 1954-, author
Thomson Wadsworth, 2004
Buku Teks