Outhwaite, William
Blackwell, 2006
Buku Teks SO
Eagleton, Clyde
New York University press, 1945
Buku Teks
Doorn, Jacques van
Faculty of Social Sciences, Erasmus University Rotterdam, 1983
Buku Teks
Anderson, Chris
House Britain Business Books, 2009
Buku Teks
Singh, Robert
Polity Press, 2002
Buku Teks