Andrew Olney Sidney K. D'Mello Natalie K. Person Whitney L. Cade Patrick Hays Claire Williams Blair Lehman Arthur C. Graesser Guru: A Computer Tutor That Models Expert Human Tutors. 256-261 2012 ITS http://dx.doi.org/10.1007/978-3-642-30950-2_32 conf/its/2012 db/conf/its/its2012.html#OlneyDPCHWLG12