"10" ALIGN="MIDDLE" BORDER="0"
 SRC="img57.png"
 ALT="$u_1 = v_1$"> and <IMG
 WIDTH="51" HEIGHT="10" ALIGN="MIDDLE" BORDER="0"
 SRC="img58.png"
 ALT="$u_2 = v_2$">, they are the same in
this case  as   the  elemental variables
and  there is  no virtue  in
exploiting  them.  Moreover  it  can happen that   although there  are
special   internal  variables,
there  are  just as   many  internal as
elemental   variables  and it therefore   doesn't particularly help to
exploit them.  For instance, if
<BR>
<DIV A