How about this one:
http://www.webmd.com/content/article/131/117956.htm
It cites a 2002 study in the American Journal of Physiology and the current recommendation of the Institute of Medicine that for a normal healthy adult it is ok to use thirst as an indicator for when to drink, that 64 ounces is a recommendation without foundation, and that caffeinated drinks work just fine for hydration.
It does note that a normal person will consumer about 60-70 ounces of liquid (and other 30-40 in food) per day but that people drinking when they're thirsty accomplish that.
It also references studies indicating that drinking water does little to directly suppress appetite and caloric intake