High Energy X-Ray Observations by HEAO-1 of the Crab Nebula, Cyg X-1, and the Galactic Center. Gruber, D. ; Matteson, J. ; Knight, F. ; Nolan, P. ; Baity, W. ; Peterson, L. ; Hoffman, J. ; Lewin, W. ; Wheaton, W. ; Primini, F. Abstract Publication: Bulletin of the American Astronomical Society Pub Date: September 1977 Bibcode: 1977BAAS....9..609G