Keeble, Richard, author
Routledge, 2001
Buku Teks
Thompson, Ian E., author
Churcill Livingstone, 1988
Buku Teks
Jencks, Charles, author
Academic Edition, 1999
Buku Teks
Tuchman, Barbara W., author
Macmillan, 1965
Buku Teks
Ayres, C.E.
Universty of Taxas Press , 1961
Buku Teks