https://archive.org/details/bstj56-10-1825/mode/1up
BSTJ 56: 10. December 1977: WT4 Millimeter Waveguide System: Introduction. (Warters, W.D.) : Free...
Bell System Technical Journal, 56: 10. December 1977 pp 1825-1827. WT4 Millimeter Waveguide System: Introduction. (Warters, W.D.)