Hidayat, A. S. E., M. Afa, and D. Kurniawan. “Modelling Crop Insurance Based on Weather Index Using The Homotopy Analysis for American Put Option”. Jurnal Varian, Vol. 4, no. 2, Apr. 2021, pp. 117 -24, doi:https://doi.org/10.30812/varian.v4i2.993.