An approximate solution of (18) can be expressed in the form
where and are respectively the Fredholm determinant and the Fredholm first minor of the kernel and are expressible as power series in b :
The coefficients can be computed by using the following relations 
Substituting from (19) and comparing the result with (8) we identify the kernel of an equivalent feed-forward operator
The application of parametric mapping leads to
where , being the Jacobian of the transformation .