Stephanie Elzer Nancy Green Sandra Carberry James Hoffman A Model of Perceptual Task Effort for Bar Charts and its Role in Recognizing Intention. 1-30 2006 16 User Model. User-Adapt. Interact. 1 http://dx.doi.org/10.1007/s11257-006-9002-9 db/journals/umuai/umuai16.html#ElzerGCH06