Byungyeon Hwang Bogju Lee An Efficient E-mail Monitoring System for Detecting Proprietary Information Outflow Using Broad Concept Learning. 72-78 http://dx.doi.org/10.1007/978-3-540-24647-3_6 2003 conf/metainformatics/2003 Metainformatics db/conf/metainformatics/metainformatics2003.html#HwangL03