With equations , and , {HEAD ~ the formula} can be approximated by {TAIL ~ the equation} ##EQU11## for i, j  
approximated by
With equations , and , { HEAD ~ the formula } can be approximated by { TAIL ~ the equation } # # EQU11 # # for i , j
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH