1. Sensiper, S., "Electromagnetic wave propagation on helical conductors,", Sc.D. Thesis, Massachusetts Institute of Technology, Cambridge, Mar. 1951.
doi:10.1063/1.1721859
2. Chodorov, M. and E. L. Chu, "Cross-wound twin helices for traveling-wave tubes," J. Appl. Phys., Vol. 26, No. 1, 33-43, 1955.
3. Watkins, D. A., Topics in Electromagnetic Theory, John Wiley & Sons, 1958.
4. Zhang, K. A. and D. L, Electromagnetic Theory for Microwaves and Optoelectronics, 2nd Ed., Springer-Verlag, 2008.
5. Basu, B. N., Electromagnetic Theory and Applications in Beamwave Electronics, World Scientific, 1996.