Search for Interstellar Scattering X-Ray Halos with HEAO-1 Scanning Modulation collimator Spada, G. ; Bradt, H. ; Doxsey, R. ; Griffiths, R. ; Gursky, H. ; Schwartz, D. ; Schwarz, J. Abstract Publication: Bulletin of the American Astronomical Society Pub Date: September 1977 Bibcode: 1977BAAS....9Q.626S