priate because they
are positive definite. 
</p>
<p>
This tool was inspired by the work of Glen Cowan together with Stephan
Horner, Sascha Caron, 
Eilam Gross, and others.  
The initial implementation is independent work.  The major step forward
in the approach was 
to provide a well defined algorithm that specifies the order of
polynomial to be included 
in the correction.  This is an empirical algorithm, so in addition to the
nominal model it 
needs either a real data set or a simulated one.  In 