G. Cautes, The approximate or exact analytical solutions for the differential equations which describe parametric free vibrations of mechanical systems, Analele Universităţii "Dunărea de Jos" din Galaţi. Fascicula XIV, Inginerie mecanică = Annals of “Dunarea de Jos“ University of Galati. Fascicle XIV, Mechanical Engineering, vol. 20, nᵒ 1, p. 65-68, juin 2013.