Phil Gordon's Little Green Book - Preflop Open Amount ... Wha?!

[Durer]

one explanation could be that he wants to play smaller pots out of position because it is harder, and that the early position raise has an inherit power because of the perception that you only raise good hands from early position. I think Thunder Keller wrote something about in Cardplayer magazine before, but i could have that wrong.

edit: Thunder Keller article CPM