Thus, one aspect of the invention is {HEAD ~ a portable device} having a main unit and {TAIL ~ a keyboard unit} 
having
Thus , one aspect of the invention is { HEAD ~ a portable device } having a main unit and { TAIL ~ a keyboard unit }
OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL