Seok-Cheol Lee Chang Soo Kim Design and Implementation of Remote Monitoring System for Supporting Safe Subways Based on USN. 321-330 2008 New Directions in Intelligent Interactive Multimedia http://dx.doi.org/10.1007/978-3-540-68127-4_34 series/sci/2008-142 db/series/sci/sci142.html#LeeK08