Jeff Yass and Ken Griffin are in a league of their own. Yass is the co-founder and managing director at the global quantitative trading firm Susquehanna International Group, while Griffin is CEO of the massive "pod shop" hedge fund Citadel. Both billionaires have built financial empires and are quite skilled at their trade.That's why investors who want to follow their leads anxiously await the quarterly 13F filings, when hedge funds like Susquehanna and Citadel disclose to the Securities and Exchange Commis ...