2012. The parametrical free vibrations of elastic systems. the analytical exact solutions. 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 (Jun. 2012), 55–58.