1. Angel, J.R.P., Astrophys. J.233, 364 (1979)
2. Baez, A.V., X-Ray Optics and X-Ray Microanalysis, Academic Press, New York (1963)
3. Dicke, R.H., Astrophys. J.153, L-101 (1968)
4. Gorenstein, P., B. Harris, H. Gursky, R. Giaconi, Nucl. Instr. Math.91, 452 (1971)
5. Johannson, A., B.L. Beron, L. Campbell, R. Eichler, R. Gorodetsky, R. Hofstadter, E.B. Hughes, S. Wilson: IEEE Trans.NS-27, 375 (1980)