1. Emslie, A., R. Lagace, and P. Strong, "Theory of the propagation of UHF radio waves in coal mine tunnels," IEEE Trans. Antennas Propag., Vol. 23, No. 2, 192-205, Mar. 1975.
2. Didascalou, D., J. Maurer, and W. Wiesbeck, "Subway tunnel guided electromagnetic wave propagation at mobile communication frequencies," IEEE Trans. Antennas Propag., Vol. 49, No. 11, 1590-1596, Nov. 2001.
3. Lienard, M. and P. Degauque, "Natural wave propagation in mine environments," IEEE Trans. Antennas Propag., Vol. 48, No. 9, 1326-1339, Sep. 2000.
4. Nikitin, P., D. D. Stancil, O. K. Tonguz, A. Cepni, A. Xhafa, and D. Brodtkorb, "Propagation model for the HVAC duct as a communication channel," IEEE Trans. Antennas Propag., Vol. 51, No. 5, 945-951, May 2003.
5. Nikitin, P., D. Stancil, A. Cepni, A. Xhafa, O. Tonguz, and D. Brodtkorb, "A novel mode content analysis technique for antennas in multimode waveguides," IEEE Trans. Microw. Theory Tech., Vol. 51, No. 12, 2402-2408, Dec. 2003.
6. Zhi, S. and I. F. Akyildiz, "Channel modeling of wireless net-works in tunnels," IEEE Global Telecommunications Conference (GLOBECOM'08), New Orleans, LA, Nov. 30-Dec. 4, 2008.
7. Martelly, R. and R. Janaswamy, "An ADI-PE approach for modeling radio transmission loss in tunnels," IEEE Trans. Antennas Propag., Vol. 57, No. 6, 1759-1770, Jun. 2009.
8. Kim, J., J. Lim, J. Friedman, U. Lee, L. Vieira, D. Rosso, M. Gerla, and M. Srivastava, "SewerSnort: A drifting sensor for in-situ sewer gas monitoring," Sixth Annual IEEE Communications Society Conference on Sensor, Mesh and Ad Hoc Communications and Networks (SECON 2009), Rome, Italy, Jun. 2009.
9. DeHaan, J. and M. Jacobs, "Tunnel communication test results," Hydroelectric Research and Technical Services Group, Bureau of Reclamation, U.S. Dept. of Interior, Sep. 1998.
10. Kjeldsen, E. and M. Hopkins, "An experimental look at RF propagation in narrow tunnels," Proc. IEEE Military Communications Conf. (MILCOM'06), Washington D.C., Oct. 23-25, 2006.
11. Howitt, I., "Monitoring systems and methods for sewer and other conduit systems ,", US Patent Pending 12/399,492.
12. Rappaport, T. S., Wireless Communications: Principles and Practice, Prentice Hall, Englewood Cliffs, NJ, 1996.
13. Bertoni, H. L., Radio Propagation for Modern Wireless Systems, Prentice Hall, Englewood Cliffs, NJ, 2000.
14. Howitt, I. L., M. S. Khan, and J. S. Khan, "A mode based model for radio wave propagation in storm drain pipes," PIERS Online, Vol. 4, No. 6, 635-640, Jul. 2008.
15. Harrington, R. F., Time Harmonic Electromagnetic Fields, McGraw-Hill, 1961.
16. Howitt, I., S. Khan, and J. Khan, "Lumped parameter radio wave propagation model for storm drain pipes," Proceedings of First International Conference on Computer, Control and Communications, Karachi, Pakistan, Nov. 12-13, 2007.
17. Khan, J., "Radio frequency propagation study in storm drain pipes,", UNCC ECE Department MS Thesis, 2007.
18. Boyd, S. and L. Vandenberghe, Convex Optimization, Cambridge University Press, 2004.
19. Shi, C., "Effect of mixing proportions of concrete on its electrical conductivity and the rapid chloride permeability test (ASTM C1202 or ASSHTO T277) results," Cement and Concrete Research, Vol. 34, 537-545, 2004.
20. Rajabipour, F., J. Weiss, and D. Abraham, "Insitu electrical conductivity measurements to assess moisture and ionic transport in concrete (a discussion of critical features that influence the measurements),", Online report available at http://cobweb.ecn.purdue.edu/»concrete/weiss/publications/o conference/OC-021.pdf.