Pepall, Lynne, author
Thomson , 2005
Buku Teks
Shepherd, William G., author
Prentice-Hall, 1979
Buku Teks
Scherer, F. M., author
Rand McNally , 1970
Buku Teks
Woodward, Joan, author
Oxford University Press, 1965
Buku Teks
Martin, Stephen, 1961-, author
Maxwell Macmillan International, 1994
Buku Teks