theorem Th57:
  (i1 ';' i2 ';' i3 ';' i4 ';' i5).4 = IncAddr(i5,4)
 proof
   LastLoc(i1 ';' i2 ';' i3 ';' i4) = 4 by Th32;
  hence thesis by Th49;
 end;
