Tal, Tomer; van Dokkum, Pieter G.; Nelan, Jenica; Bezanson, Rachel (1 November 2009). "The Frequency of Tidal Features Associated with Nearby Luminous Elliptical Galaxies From a Statistically Complete Sample". The Astronomical Journal. 138 (5): 1417–1427. arXiv:0908.1382. Bibcode:2009AJ....138.1417T. doi:10.1088/0004-6256/138/5/1417. S2CID19104100.
Welch, Gary A.; Sage, Leslie J.; Young, Lisa M. (10 December 2010). "The Cool Interstellar Medium in Elliptical Galaxies. II. Gas Content in the Volume-limited Sample and Results from the Combined Elliptical and Lenticular Surveys". The Astrophysical Journal. 725 (1): 100–114. arXiv:1009.5259. Bibcode:2010ApJ...725..100W. doi:10.1088/0004-637X/725/1/100. S2CID119241814.
Seligman, Courtney. "NGC 3640". Celestial Atlas. Retrieved 19 November 2018.
doi.org
Tal, Tomer; van Dokkum, Pieter G.; Nelan, Jenica; Bezanson, Rachel (1 November 2009). "The Frequency of Tidal Features Associated with Nearby Luminous Elliptical Galaxies From a Statistically Complete Sample". The Astronomical Journal. 138 (5): 1417–1427. arXiv:0908.1382. Bibcode:2009AJ....138.1417T. doi:10.1088/0004-6256/138/5/1417. S2CID19104100.
Welch, Gary A.; Sage, Leslie J.; Young, Lisa M. (10 December 2010). "The Cool Interstellar Medium in Elliptical Galaxies. II. Gas Content in the Volume-limited Sample and Results from the Combined Elliptical and Lenticular Surveys". The Astrophysical Journal. 725 (1): 100–114. arXiv:1009.5259. Bibcode:2010ApJ...725..100W. doi:10.1088/0004-637X/725/1/100. S2CID119241814.
Tal, Tomer; van Dokkum, Pieter G.; Nelan, Jenica; Bezanson, Rachel (1 November 2009). "The Frequency of Tidal Features Associated with Nearby Luminous Elliptical Galaxies From a Statistically Complete Sample". The Astronomical Journal. 138 (5): 1417–1427. arXiv:0908.1382. Bibcode:2009AJ....138.1417T. doi:10.1088/0004-6256/138/5/1417. S2CID19104100.
Prugniel, P.; Nieto, J.L.; Bender, R.; Davoust, E. (October 1988). "The 'normal' elliptical galaxy NGC 3640 - A merger in progress?". Astronomy and Astrophysics. 204 (1–2): 61–67. Bibcode:1988A&A...204...61P. ISSN0004-6361.
Welch, Gary A.; Sage, Leslie J.; Young, Lisa M. (10 December 2010). "The Cool Interstellar Medium in Elliptical Galaxies. II. Gas Content in the Volume-limited Sample and Results from the Combined Elliptical and Lenticular Surveys". The Astrophysical Journal. 725 (1): 100–114. arXiv:1009.5259. Bibcode:2010ApJ...725..100W. doi:10.1088/0004-637X/725/1/100. S2CID119241814.
Tal, Tomer; van Dokkum, Pieter G.; Nelan, Jenica; Bezanson, Rachel (1 November 2009). "The Frequency of Tidal Features Associated with Nearby Luminous Elliptical Galaxies From a Statistically Complete Sample". The Astronomical Journal. 138 (5): 1417–1427. arXiv:0908.1382. Bibcode:2009AJ....138.1417T. doi:10.1088/0004-6256/138/5/1417. S2CID19104100.
Welch, Gary A.; Sage, Leslie J.; Young, Lisa M. (10 December 2010). "The Cool Interstellar Medium in Elliptical Galaxies. II. Gas Content in the Volume-limited Sample and Results from the Combined Elliptical and Lenticular Surveys". The Astrophysical Journal. 725 (1): 100–114. arXiv:1009.5259. Bibcode:2010ApJ...725..100W. doi:10.1088/0004-637X/725/1/100. S2CID119241814.
Prugniel, P.; Nieto, J.L.; Bender, R.; Davoust, E. (October 1988). "The 'normal' elliptical galaxy NGC 3640 - A merger in progress?". Astronomy and Astrophysics. 204 (1–2): 61–67. Bibcode:1988A&A...204...61P. ISSN0004-6361.