Therefore, {HEAD ~ the grass} can be mown, without leaving {TAIL ~ any uncut grasses}, so as to have a good finish 
mown without leaving
Therefore , { HEAD ~ the grass } can be mown , without leaving { TAIL ~ any uncut grasses } , so as to have a good finish
OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH REL OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH