Wylde, R.J.: 'Millimetre-wave Gaussian beam-mode optics and corrugated feed horns', IEE Proceedings H (Microwaves, Optics and Antennas), 1984, 131, (4), p. 258-262, DOI: 10.1049/ip-h-1.1984.0053
IET Digital Library, https://digital-library.theiet.org/;jsessionid=1rn1fc3exdfsd.x-iet-live-01content/journals/10.1049/ip-h-1.1984.0053