@article {IOPORT.50301144,
    author       = {Xu, Xiubin and Pan, Yunlan and Small, Robert D.},
    title        = {Nonlinear approximations to the derivative of delta function},
    year         = {2007},
    journal      = {Applied Mathematics and Computation},
    volume       = {185},
    number       = {1},
    pages        = {583-593},
    doi          = {10.1016/j.amc.2006.07.049},
    identifier   = {50301144},
}