E. López Meneses, and A. Infante Moro. DIM: Didáctica, Innovación y Multimedia, (2010)Available at http://www.raco.cat/index.php/DIM/article/viewArticle/214696/0.
J. Tang, T. Wang, and J. Wang. Proceedings of the 2008 The 9th International Conference for Young Computer Scientists, page 1664--1670. Washington, DC, USA, IEEE Computer Society, (2008)
E. López Meneses, and M. Lorente Cejudo. Educatio siglo XXI, (2010)Available at http://digitum.um.es/xmlui/handle/10201/27105?mode=full&submit\_simple=Show+full+item+record.