HEAO-1 Observations of Compact Extragalactic X-Ray Sources. Mushotzky, R. F. ; Boldt, E. A. ; Holt, S. S. ; Rothschild, R. ; Serlemitsos, P. J. Abstract Publication: Bulletin of the American Astronomical Society Pub Date: June 1978 Bibcode: 1978BAAS...10..503M