Can anybody tell me where it is written that pre flop, the minimum raise or bet, in No limit Texas Hold'em Tournaments has to be equivalent to double the big blind. I've searched the internet, I can find alot of info on raises once a bet has been made but can't find it written in regards to pre flop raises. I need it to be some sort of official site such as WSOP, Tournament Directors of America, World Poker Tour or at least something resembling something official.