For a summary of the approach by W. Domhoff and CW Mills on the upper class as a small undemocratic group they named 'the power elite'.
http://www.political-reform.net/power_elite.htm
C W Mills used the phrase 'the revolving door' (between the political, the economic, and the military bases of this elite/upper class)
They were writing in the 1960s you could bring their analysis up to date by examining the company Haliburton.See this ref for how to do this
http://www.lewrockwell.com/orig/felkins1.html