Cristian Bernareggi Piero Mussio Loredana Parasiliti Provenza Toward multimodal notation for mathematics: Why and how. 326-340 2009 20 J. Vis. Lang. Comput. 5 http://dx.doi.org/10.1016/j.jvlc.2009.07.006 db/journals/vlc/vlc20.html#BernareggiMP09