{TAIL ~ Two exemplary types} of {HEAD ~ service level layers} are peak signal to noise ratio layers and bitrate layers 
{ TAIL ~ Two exemplary types } of { HEAD ~ service level layers } are peak signal to noise ratio layers and bitrate layers
TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH