function c = idwts( s, n, m )
 % Build weights c(j,k) such that 
 % f(s) = \sum_{j=1}^n c( j, 1 ) f( j - 1 )
 % f'(s) = (1/h) \sum_{j=1}^n c( j, 2 ) f( j - 1 )
 % f''(s) = (1/h^2) \sum_{j=1}^n c( j, 3 ) f( j - 1 )
 % ...
 % f^(m-1)(s) = (1/h^{m-1})\sum_{j=1}^n c( j, m ) f( j - 1 )
 % for polynomials f of maximum possible degree.
 c1 = 1.0;
 c4 = -s;
 c = zeros( n, m );
 c( 1, 1 ) = 1.0;
 for i = 1 : n - 1
  c2 = 1.0;
  c5 = c4;
  c4 = i - s;
  for j = 0 : i - 1
   c3 = i - j;
   c2 = c2 * c3;
   for k = min( i, m - 1 ) : -1 : 1
    c( i + 1, k + 1 ) = c1 * ( k * c( i, k ) - c5 * c( i, k + 1 ) ) / c2;
   end
   c( i + 1, 1 ) = -c1 * c5 * c( i, 1 ) / c2;
   for k = min( i, m - 1 ) : -1 : 1
    c( j + 1, k + 1 ) = ( c4 * c( j + 1, k + 1 ) - k * c( j + 1, k ) ) / c3;
   end
   c( j + 1, 1 ) = c4 * c( j + 1, 1 ) / c3;
  end
  c1 = c2;
 end
end