@article{ramirez_hasselmann_zhang_2011,  title={Channel characteristics in tunnels: FDTD simulations and measurement},  volume={10},  ISSN={2179-1074},  url={https://doi.org/10.1590/S2179-10742011000100013},  DOI={10.1590/S2179-10742011000100013},  number={1},  journal={Journal of Microwaves, Optoelectronics and Electromagnetic Applications},  publisher={Sociedade Brasileira de Microondas e Optoeletrônica e Sociedade Brasileira de Eletromagnetismo},  author={Ramirez, L.A.R. and Hasselmann, F.J.V. and Zhang, Y.P.},  year={2011},  month={Jun},  pages={121–130} }