1. Soft X-radiation in the upper atmosphere;Burnight;Phys. Rev.,1949
2. Observations at high altitudes of extreme ultraviolet and X-rays from the Sun;Purcell;Phys. Rev.,1949
3. Evidence for X-rays from sources outside the Solar System;Giacconi;Phys. Rev. Lett.,1962
4. Lunar X-rays and the cosmic X-ray background measured by the lunar satellite Luna-12;Mandel'shtam;Cosmic Res. (USSR),1968
5. Further evidence for the existence of galactic X-rays;Gursky;Phys. Rev. Lett.,1963