Notice of Retraction: The Research and Implementation of Distance Learning Based on 3G Network - Yu, Feng; Zhao, Ji-chun; Zhang, Ju-feng; Sun, Su-fen; Guo, Jian-xin; Zhao, You-sen (2009 First International Conference on Information Science and Engineering, Information Science and Engineering (ICISE), 2009 1st International Conference on, 2009)