z=poly(0,'z');
 diary(0)
 diary('spfact1.dia')
a=[ -0.09-0.35z+z^2 ,-0.02-0.13z
   -0.03-0.15z     ,  -0.08-0.36z+z^2  ]
 diary(0)
 diary('spfact2.dia') 
  sp=a*tild(a)
 diary(0)
 diary('spfact3.dia') 
  d=sfact(sp)
 diary(0)
 diary('spfact4.dia') 
  sp-d*tild(d)
