{HEAD ~ Such an equation} can also be used directly for {TAIL ~ the 3 D reference model} during run time, as further described below 
used directly for
{ HEAD ~ Such an equation } can also be used directly for { TAIL ~ the 3 D reference model } during run time , as further described below
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH