Calvocoressi, Peter
Longman, 1991
Buku Teks
Vanhanen, Tatu, author
Routledge, 1997
Buku Teks
Rourke, John T., author
Brooks/Cole, 1986
Buku Teks
Mansbach, Richard W., author
Houghton Miffiln, 2000
Buku Teks
Follett, ken, author
Pan Books, 2014
Buku Teks