FIG 1 illustrates {TAIL ~ the basic principle} of {HEAD ~ the trace} according to the invention 
FIG 1 illustrates { TAIL ~ the basic principle } of { HEAD ~ the trace } according to the invention
OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH