Openshaw, H.T.
Cambridge University Press, 1962
Buku Teks
Silverman, David, author
Sage Publications , 2010
Buku Teks
Silverman, David, author
Sage, 2000
Buku Teks
Sage Publications, 2008
eBooks
Haenssgen, Marco J., author
Emerald Publishing Limited, 2019
eBooks