USSR HAM-Radio CallBook in 1926

I just found a very interesting paper - a complete list of all transmitting amateur radio stations in 1926 in the USSR, club stations, as well as personal ones. It is remarkable, that the frequencies and power levels of club stations are selected in such a way that ensures reliable traffic between distant regions and Moscow - the farther station from center, the higher its power and shorter its wavelength. And another note - individuals had managed to use different wavelengths, so it was not too easy to contact each other that times.