Dokmaisot, author
Southeart Asia Program, 1992
Buku Teks
Ruml, Bearsdsley
McGraw-Hill, 1959
Buku Teks
Beardsley, Monroe C.
Prentice-Hall, 1963
Buku Teks
edited by Sam Smiles and Stephanie Moser
Blackwell Publishing, 2005
Buku Teks
Acton, Edward
Longman, 1986
Buku Teks