Vince Kellen Susy S. Chan Xiaowen Fang Facilitating Conditional Probability Problems with Visuals. 63-71 2007 conf/hci/2007-2 HCI (2) http://dx.doi.org/10.1007/978-3-540-73107-8_8 db/conf/hci/hci2007-2.html#KellenCF07