Audit firm reference help please..

Hi all! 

I am a CA passed out in May 2011 and continuing in my firm since then. I want to join in

bigger audit firms (big 4s and the next level of firms). But I donot personally know 

anybody from any of these firms. I heard that they hire only on reference. Can anybody 

working in firms like PWC, E n Y, Deloitte, Sharpe and Tannan, and other similar firms

help me by refering?