Comparative analysis of linear and non-linear free vibrations of harmonic oscillator Khusen Kulterbaev, Valentina Vodakhova, Lyalusya Baragunova, Marina Dadova and Mariana Shogenova E3S Web Conf., 281 (2021) 01028 Published online: 02 July 2021 DOI: 10.1051/e3sconf/202128101028