High-order correlation function

Hello,

In Section 4 of:

S.A. Billings, W.S.F. Voon (1983), Structure detection and model validity tests in the identification of nonlinear systems, IEE Proceedings, Vol. 130, No. 4, JULY 1983.

The authors use a high-order correlation function applied to the response signal performed in a linear identification. Then, if the result is within the confidence inteval of 95% means that the system is linear.

How can I implement the function described by Billings e Voon in matlab? If I'm not mistaken ,I will need to use a FIR model, is not it?

Can someone help me with this ?

Thanks