NED NGC 3003. Jet Propulsion Laboratory, California Institute of Technology. "Results for NGC 3003". NASA/IPAC Extragalactic Database. National Aeronautics and Space Administration. Retrieved 23 October 2012.
NED NGC 3344. Jet Propulsion Laboratory, California Institute of Technology. "Results for NGC 3344". NASA/IPAC Extragalactic Database. National Aeronautics and Space Administration. Retrieved 23 October 2012.
NED NGC 3504. Jet Propulsion Laboratory, California Institute of Technology. "Results for NGC 3504". NASA/IPAC Extragalactic Database. National Aeronautics and Space Administration. Retrieved 23 October 2012.
NED NGC 3486. Jet Propulsion Laboratory, California Institute of Technology. "Results for NGC 3486". NASA/IPAC Extragalactic Database. National Aeronautics and Space Administration. Retrieved 23 October 2012.
NED NGC 2859. Jet Propulsion Laboratory, California Institute of Technology. "Results for NGC 2859". NASA/IPAC Extragalactic Database. National Aeronautics and Space Administration. Retrieved 23 October 2012.
Keenan, Philip C.; McNeil, Raymond C. (1989). "The Perkins Catalog of Revised MK Types for the Cooler Stars". The Astrophysical Journal Supplement Series. 71: 245. Bibcode:1989ApJS...71..245K. doi:10.1086/191373.
Keenan, Philip C.; McNeil, Raymond C. (1989). "The Perkins Catalog of Revised MK Types for the Cooler Stars". The Astrophysical Journal Supplement Series. 71: 245. Bibcode:1989ApJS...71..245K. doi:10.1086/191373.