    ( r  r  r  r  r  v2 v2 )
       ( u1 t  t  v1 v1 )       ( r  r  r  r  r  r  v2 )
   Q = ( u1 u1 r  q  q  ),  B = ( b  b  b  r  r  b  b  ).
       ( u1 u1 r  q  q  )       ( b  b  b  r  r  b  b  )
       ( u1 u1 r  q  q  )       ( b  b  b  r  r  b  b  )

  where a, b, g and q denote elements of the original matrices, r
  denotes a modified element, t denotes a scalar factor of an
  applied elementary reflector, ui and vi denote elements of the
  matrices U and V, respectively.

</PRE>
<A name="Numerical