Lan, Shih-Hao; Kong, Albert K. H.; Verbunt, Frank; Lewin, Walter H. G.; Bassa, Cees; Anderson, Scott F.; Pooley, David (2010), "X-Ray and Optical Study of Low Core Density Globular Clusters Ngc6144 and E3", The Astrophysical Journal, 712: 380–391, arXiv:0907.0837, doi:10.1088/0004-637X/712/1/380, S2CID11046118
Lan, Shih-Hao; Kong, Albert K. H.; Verbunt, Frank; Lewin, Walter H. G.; Bassa, Cees; Anderson, Scott F.; Pooley, David (2010), "X-Ray and Optical Study of Low Core Density Globular Clusters Ngc6144 and E3", The Astrophysical Journal, 712: 380–391, arXiv:0907.0837, doi:10.1088/0004-637X/712/1/380, S2CID11046118
Lan, Shih-Hao; Kong, Albert K. H.; Verbunt, Frank; Lewin, Walter H. G.; Bassa, Cees; Anderson, Scott F.; Pooley, David (2010), "X-Ray and Optical Study of Low Core Density Globular Clusters Ngc6144 and E3", The Astrophysical Journal, 712: 380–391, arXiv:0907.0837, doi:10.1088/0004-637X/712/1/380, S2CID11046118