Optical studies of UHURU sources. XI. A probable period for Scorpius X-1 = V818 Scorpii. Gottlieb, E. W. ; Wright, E. L. ; Liller, W. Abstract Publication: The Astrophysical Journal Pub Date: January 1975 DOI: 10.1086/181703 Bibcode: 1975ApJ...195L..33G