Jahna Otterbacher Dragomir R. Radev Omer Kareem Hierarchical summarization for delivering information to mobile devices. 931-947 2008 44 Inf. Process. Manage. 2 http://dx.doi.org/10.1016/j.ipm.2007.06.002 db/journals/ipm/ipm44.html#OtterbacherRK08