1. Hines, M. E. Channel separation filter, U.S. Patent 2,651,715, September 8, 1953.
2. Goubau, G. Transmission of electromagnetic wave beams. U.S. Patent 3,101,472, August 20, 1963.
3. Goubau, G., and Christian, J. R. A new waveguide for millimeter waves. Proc. Army Sci. Conf., U.S. Military Acad., West Point, New York, June 1959, 1, 291–303. Publ. by Dept. of the Army, Washington, D.C., 1960.
4. Experimental studies on a beam waveguide for millimeter waves;Christian;IRE Trans. Antennas Propagation,1961