E.H. Carr.The Twenty Year's Crisis (London: Macmillan. 1962). p. 107.
2.
Hedley Bull. 'International Theory : The Case for the Classical Approach'. in K. Knorr and J. Rosenau (eds.). Contending Approaches to International Politics (Princeton. NJ: Princeton University Press, 1966). pp. 20-38.
3.
Ibid, p. 22.
4.
Thcda Skocpol. "Wallerstein's World Capitalist System: A Theoretical and Historical Critique', American Journal of Sociology (Vol. 82, No. 5, 1977), pp. 1075-90.