X-Ray Variability of Seyfert Galaxies Observed with the Einstein Observatory Urry, C. M. ; Canizares, C. R. ; Kruper, J. S. ; Rohan, M. L. ; Oberhardt, M. R. Abstract Publication: Bulletin of the American Astronomical Society Pub Date: September 1986 Bibcode: 1986BAAS...18.1000U