Much research has been conducted on the development of a measure of anesthetic depth. A device that measured the bispectral index (BIS) is on the market and has been used in some feedback-control studies. Perform a literature search and discuss at least two papers that present feedback-control results based on a BIS measurement and the manipulation of either an intravenous (such as propofol) or vapor-phase (such as isoflurane) anesthetic. | 
