For {HEAD ~ experienced users}, cues are rendered so that at any time {TAIL ~ the user} can say a desired keyword to invoke the corresponding application 
For { HEAD ~ experienced users } , cues are rendered so that at any time { TAIL ~ the user } can say a desired keyword to invoke the corresponding application
OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH