Amri, I., N. Chamidah, T. Saifudin, B. Lestari, D. Aydin, and F. Rohim. “A Penalized Least Squares Estimation of Fourier Series Semiparametric Regression Theory, Simulation, and Application”. Statistics, Optimization & Information Computing, Feb. 2026, doi:10.19139/soic-2310-5070-3139.