Knox, Paul, author
Edward Arnold , 1994
Buku Teks
by Les Rowntree ... [and others]
Prentice-Hall, 2011
Buku Teks
by Les Rowntree ... [and others]
Prenticel Hall, 2008
Buku Teks
Cole, J.P., author
Penguin Books, 1979
Buku Teks
De Blij, Harm J., author
John Wiley & Sons, 2010
Buku Teks