Pasarella, M., S. Sifriyani, and F. Amijaya. “NONPARAMETRIK REGRESSION MODEL ESTIMATION WITH THE FOURIER SERIES THE FOURIER SERIES APPROACH AND ITS APPLICATION TO THE ACCUMULATIVE COVID-19 DATA IN INDONESIA”. BAREKENG: Jurnal Ilmu Matematika Dan Terapan, Vol. 16, no. 4, Dec. 2022, pp. 1167-74, doi:10.30598/barekengvol16iss4pp1167-1174.