Gowland, David
Harvester Wheatsheaf, 1991
Buku Teks
Carlberg, Michael
Springer, 2012
eBooks
by Charles C. Holt ... [et al.]
Urban Institute Press, 1971
Buku Teks SO
Weintraub, Sidney
Addison-Wesley, 1978
Buku Teks SO
Layard, Richard
Oxford University Press, 1992
Buku Teks SO