T. R. Muzaki, E. Siswanah, and S. D. Miasary, “Calculation of Tabarru Funds Using Makeham’s Mortalita Law and Gompertz’s Mortalita Law Using the Cost Of Insurance Method”, J. Nat. Scien. & Math. Res., vol. 6, no. 1, pp. 38–42, Jun. 2020.