Iqbal, W. (2021) “Parametric and Non-Parametric Spectral Signal Processing Techniques for Estimation of Periodicity in Sunspot Numbers: Spectral signal processing techniques for estimation of preiodcity in sun spot numbers”, Proceedings of the Pakistan Academy of Sciences: A. Physical and Computational Sciences, 56(1), pp. 9–20. Available at: http://ppaspk.org/index.php/PPAS-A/article/view/146 (Accessed: 4 December 2025).