{HEAD ~ a user interface} for receiving user input to enable tracking wherein {TAIL ~ the user input} is received via a user interface that enables the user to manually enable tracking, to disable tracking or enable automatic triggering of tracking 
wherein
{ HEAD ~ a user interface } for receiving user input to enable tracking wherein { TAIL ~ the user input } is received via a user interface that enables the user to manually enable tracking , to disable tracking or enable automatic triggering of tracking
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH