Feng Jing Kang ShiYing Research of Study Evaluation in E-learning System Based on UD and RBPNN. 573-576 2008 CSSE (5) http://dx.doi.org/10.1109/CSSE.2008.1429 conf/csse/2008-5 db/conf/csse/csse2008-5.html#JingS08