D. A. de Waal, S. E. S. Campher, and J. V. du Toit. 2012. “Estimating Those Transformations That Produce the Best-Fitting Additive Model: Smoothers Versus Universal Approximators”. International Journal of Computer Information Systems and Industrial Management Applications 4 (January):9. https://cspub-ijcisim.org/index.php/ijcisim/article/view/145.