said {HEAD ~ second wearable display} has a same constitution as {TAIL ~ the first wearable display comprises}: 
said { HEAD ~ second wearable display } has a same constitution as { TAIL ~ the first wearable display comprises } :
OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH