Pugh, Eric, author
Oryx Press, 1981
Buku Referensi
Johnson, William M., author
Delmar, 1997
Buku Teks
Orna, Elizabeth, author
Gower, 1999
Buku Teks
Veryard, Richard, author
Prentice-Hall, 1992
Buku Teks
Henczel, Susan, author
Saur Verlag, 2001
Buku Teks