Ashraf, M. M., M. O. Ullah, T. N. Malik, A. B. Waqas, M. Iqbal, and F. Siddiq. “Robust Extraction of Harmonics Using Heuristic Advanced Gravitational Search Algorithm-Based Least Square Estimator”. The Nucleus, vol. 54, no. 4, Jan. 2018, pp. 219-31, doi:10.71330/thenucleus.2017.273.