Fahmi, M. M., J. A. Ruiz-Cruz, R. R. Mansour, and K. A. Zaki,  "Compact Wide-Band Ridge Waveguide Dual-Band Filters",  2010 IEEE MTT-S International Microwave Symposium Digest, pp. 888-891, May, 2010.

Fahmi, M. M., J. A. Ruiz-Cruz, K. A. Zaki, and R. R. Mansour,  "Compact Ridge Waveguide Filters using Non-resonating Nodes",  2009 IEEE MTT-S International Microwave Symposium Digest, pp. 1337-1340, June, 2009.

Fahmi, M. M., J. A. Ruiz-Cruz, R. R. Mansour, and K. A. Zaki,  "Compact Ridge Waveguide Filters With Arbitrarily Placed Transmission Zeros Using Nonresonating Nodes",  IEEE Transactions on Microwave Theory and Techniques, vol. 57, no. 12, pp. 3354-3361, Dec., 2009.

Ruiz-Cruz, J. A., M. A. El Sabbagh, K. A. Zaki, J. M. Rebollar, and Y. Zhang,  "Canonical ridge waveguide filters in LTCC or metallic resonators",  IEEE Transactions on Microwave Theory and Techniques, vol. 53, no. 1, pp. 174-182, Jan., 2005.