Openshaw, H.T.
Cambridge University Press, 1962
Buku Teks
John Wiley & Sons, 1980
Buku Teks
Holum, John R., author
John Wiley & Sons, 1990
Buku Teks
Holum, John R., author
John Wiley & Sons, 1982
Buku Teks
Mee, A.J.
J.M. Dent and Sond , 1960
Buku Teks