Therefore, when a given symbol of interest is considered, {HEAD ~ the other symbols} of {TAIL ~ interest} may be considered as interfering symbols 
Therefore , when a given symbol of interest is considered , { HEAD ~ the other symbols } of { TAIL ~ interest } may be considered as interfering symbols
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH