https://123dok.net/document/yev6g0ez-joint-meeting-of-the-international-scientific-radio-union-u-s-a-national-committee-and-the-professional-group-on-antennas-and-wave-propagation-of-the-institute-of-radio-engineers-held-at-washington-d-c-april-17-18-and-19-1950.html