I. Mizuuchi, M. Inaba, and H. Inoue. Intelligent Robots and Systems, 2001. Proceedings. 2001 IEEE/RSJ International Conference on, 4, page 2099--2104. IEEE, (2001)
R. Ribaldo, A. Akabane, L. Rino, and T. Pardo. Computational Processing of the Portuguese Language, volume 7243 of Lecture Notes in Computer Science, Springer Berlin Heidelberg, (2012)