Jalil Rashidinia and  Reza Jalilian,  Non-Polynomial Spline Solution of Fourth-Order Obstacle Boundary-Value Problems.   journal   = {International Journal of Mathematical and Computational Sciences}, [online]. World Academy of Science, Engineering and Technology.
    April 2009, vol. 28(4). 241 - 247
    [viewed 25 January 2020]. Available from: https://publications.waset.org/pdf/1642.