EB_CS                   Main function used in the paper (Du and Hu,
                        2022)
density_LS              log-density derivatives-parametric approach
density_PLS             Penalized least-squares method in Du and Hu
                        (2022)
density_g_model         The l_1 to l_4 derivative from the g-modeling
                        method
predictive_recursion    Predictive recursion by Newton (2002)
