{HEAD ~ These operations} of {TAIL ~ vertical and horizontal edges} can be expanded to have coefficients of a, −a, 0, or aj as before 
of
{ HEAD ~ These operations } of { TAIL ~ vertical and horizontal edges } can be expanded to have coefficients of a , −a , 0 , or aj as before
HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH