Therefore, the optical discs of two kinds in which {HEAD ~ the recording layers} are placed at {TAIL ~ different distances} can precisely be recorded or reproduced, respectively 
Therefore , the optical discs of two kinds in which { HEAD ~ the recording layers } are placed at { TAIL ~ different distances } can precisely be recorded or reproduced , respectively
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH