The parametrical free vibrations of elastic systems. the analytical exact solutions. (2012). Analele Universităţii "Dunărea de Jos" Din Galaţi. Fascicula XIV, Inginerie Mecanică = Annals of “Dunarea de Jos“ University of Galati. Fascicle XIV, Mechanical Engineering, 19(1), 55-58. https://ojs.ugal.ro/index.php/im/article/view/3694