Joan Mas, J.A. Jorge, Gemma Sanchez, & Josep Llados. (2008). Representing and Parsing Sketched Symbols using Adjacency Grammars and a Grid-Directed Parser. In J.M. Ogier J. L. W. Liu (Ed.), Graphics Recognition: Recent Advances and New Opportunities, (Vol. 5046, pp. 176–187). LNCS.