  associated with T is not (numerically) positive
                definite in its leading (P+S)*K-by-(P+S)*K part.

</PRE>
<A name="Method"><B><FONT SIZE="+1">Method</FONT></B></A>
<PRE>
  Householder transformations and modified hyperbolic rotations
  are used in the Schur algorithm [1], [2].

</PRE>
<A name="References"><B><FONT SIZE="+1">References</FONT></B></A>
<PRE>
  [1] Kailath, T. and Sayed, A.
      Fast Reliable Algorithms for Matrices with Structure.
      SIAM Publications, Philadelphia, 1999.
