1. A.E.Goddard: Proceedings of Thru-the-Earth Electromagnetics Workshop, Colo. School of Mines, Golden, Colo., 15–17 August 1973, Available from National Technical Information Service, Alexandria, VA
2. A.G.Emslie, R.L.Lagace, P.F.Strong: Proceedings of Thru-the-Earth Electromagnetic Workshop, Colo. School of Mines, Golden, Colo., 15–17 August 1973, Available from National Technical Information Service, Alexandria, VA
3. P.Delogne, L.Deryck, R.Liegeois: Proceedings of Thru-the-Earth Electromagnetics Workshop, Colo. School of Mines, Golden, Colo., 15–17 August 1973, Available from National Technical information Service, Alexandria, VA
4. J.R.Wait:Electromagnetic Radiation from Cylindrical Structures (Pergamon Press, Oxford 1959)
5. S.F.Mahmoud: Characteristics of EM guided waves for communication in coal mine tunnels, submitted to IEEE Trans. on. Communication, February 1974