R. Solea, U. Nunes, A. Filipescu, and D. Cernega, “Sliding Mode Control for Trajectory Tracking of an Intelligent Wheelchair”, The Annals of “Dunarea de Jos“ University of Galati. Fascicle III, Electrotechnics, Electronics, Automatic Control, Informatics, vol. 32, no. 2, pp. 42-50, Nov. 2009.