Gorzelańczyk, Piotr. “Method of Fundamental Solutions and Random Numbers for the Torsion of Bars With Multiply Connected Cross Sections”. Computer Assisted Methods in Engineering and Science, vol. 17, no. 2/3/4, Jan. 2017, pp. 99-112, https://cames3.ippt.pan.pl/index.php/cames/article/view/126.