Chodil, G.; Rodrigues, Hans; Seward, F.; Swift, C. D.; Hiltner, W. A.; Wallerstein, George; Mannery, Edward J. (1967), «Spectral and Location Measurements of Several Cosmic X-Ray Sources Including a Variable Source in Centaurus», Physical Review Letters19 (11): 681-683, Bibcode:1967PhRvL..19..681C, doi:10.1103/PhysRevLett.19.681.
Chodil, G.; Rodrigues, Hans; Seward, F.; Swift, C. D.; Hiltner, W. A.; Wallerstein, George; Mannery, Edward J. (1967), «Spectral and Location Measurements of Several Cosmic X-Ray Sources Including a Variable Source in Centaurus», Physical Review Letters19 (11): 681-683, Bibcode:1967PhRvL..19..681C, doi:10.1103/PhysRevLett.19.681.