Long-Term Variability of Cir X-1 and Aql X-1 as Observed by the Ariel-5 All-Sky Monitor. Kaluzienski, L. J. ; Holt, S. S. ; Boldt, E. A. ; Serlemitsos, P. J. Abstract Publication: Bulletin of the American Astronomical Society Pub Date: September 1976 Bibcode: 1976BAAS....8..541K