Timothy Read Elena Bárcena Beatriz Barros Raquel Varela Jesús Pancorbo COPPER: Modeling User Linguistic Production Competence in an Adaptive Collaborative Environment. 144-153 2005 conf/um/2005 User Modeling http://dx.doi.org/10.1007/11527886_19 db/conf/um/um2005.html#ReadBBVP05