Les Nelson Christoph Held Peter Pirolli Lichan Hong Diane J. Schiano Ed H. Chi With a little help from my friends: examining the impact of social annotations in sensemaking tasks. 1795-1798 2009 CHI http://doi.acm.org/10.1145/1518701.1518977 conf/chi/2009 db/conf/chi/chi2009.html#NelsonHPHSC09