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