The HEAO-1 Sky Survey Sub-Catalog of Bright, Hard X-ray Emitting BL Lac Objects Schwartz, D. A. ; Brissenden, R. J. V. ; Tuohy, I. R. ; Feigelson, E. D. ; Hertz, P. L. ; Remillard, R. A. Abstract Publication: Bulletin of the American Astronomical Society Pub Date: March 1989 Bibcode: 1989BAAS...21R.777S