Babenko, V. F., and D. A. Levchenko. “Uniformly Distributed Ridge Approximation of Some Classes of Harmonic Functions”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 64, no. 10, Oct. 2012, pp. 1426-31, https://umj.imath.kiev.ua/index.php/umj/article/view/2669.