Stanescu, N., A.-F. Stan, and N. Pandrea. “On the Dynamics of the Constrained Rigid Solid Acted by Conservative Forces. Part I: Theory”. Romanian Journal of Acoustics and Vibration, Vol. 17, no. 1, July 2020, pp. 3-9, http://rjav.sra.ro/index.php/rjav/article/view/150.