  The orthogonal derivative is defined as a limit of an integral whose kernel
contains an orthogonal polynomial with its measure. When in practice no limit
is taken, it means that the accuracy of the derivative depends on the second
derivative of the given function. Liptaj shows that it is possible to define a
kernel in such a way that the accuracy depends on a higher derivative at your
own choice. The accuracy is therefore much greater than with the orthogonal
derivative. However Diekema and Koornwinder find a similar extension starting
directly from of the orthogonal derivative. The new kernel is not orthogonal
for order greater then one. The transfer function for this new derivative is
given.
