A history is presented of measurements of solar vacuum uv and soft x radiation made by rocket and satellite-borne instruments in the U.S.S.R. The origin and mechanism of the production of solar x rays are discussed.
S. L. Mandelstam, "Studies of Shortwave Solar Radiation in the U.S.S.R.," Appl. Opt. 6, 1834-1844 (1967)