6Chakib Baouche, Antonio Freitas, Michel Misson. Radio Proximity Detection in a WSN to Localize Mobile Entities Within a Confined Area [J]. Journal of Communications, 2009 (4):232- 240.
7Akyildiz I F, Stuntebeck E P. Wireless Underground Sensor Networks : Research Challenges [ J ]. Ad Hoc Networks ( Elsevier), 2006 (6) : 669-686.
8Akyildiz l F, Sun Z, Vuran M C. Signal Propagation Tech- niques for Wireless Underground Communication Networks [ J]. Physical Communication (Elsevier) Journal, 2009 (3): 167- 183.
9Yan Wu, Min Lin, Ian J Wassell. Modified 2D Finite-Difference Time-Domain Based Tunnel Path Loss Prediction for Wire- less Sensor Network Applications [ J ]. Joumal of Communications, 2009 (4) : 214-223.
10Mo, LIU Yun-hao. Underground Coal Mine Monitoring with Wireless Sensor Networks [ J ]. ACM Transactions on Sensor Networks, 2009 (2): 1-9.
