Macri, L. M. (2006). "A New Cepheid Distance to the Maser-Host Galaxy NGC 4258 and Its Implications for the Hubble Constant". The Astrophysical Journal. 652 (2): 1133–1149. arXiv:astro-ph/0608211. Bibcode:2006ApJ...652.1133M. doi:10.1086/508530.Parameter |coauthors= yang tidak diketahui mengabaikan (|author= yang disarankan) (bantuan)
Macri, L. M. (2006). "A New Cepheid Distance to the Maser-Host Galaxy NGC 4258 and Its Implications for the Hubble Constant". The Astrophysical Journal. 652 (2): 1133–1149. arXiv:astro-ph/0608211. Bibcode:2006ApJ...652.1133M. doi:10.1086/508530.Parameter |coauthors= yang tidak diketahui mengabaikan (|author= yang disarankan) (bantuan)
"The Odd Couple". ESO Press Release. Diakses tanggal 8 August 2013.
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Macri, L. M. (2006). "A New Cepheid Distance to the Maser-Host Galaxy NGC 4258 and Its Implications for the Hubble Constant". The Astrophysical Journal. 652 (2): 1133–1149. arXiv:astro-ph/0608211. Bibcode:2006ApJ...652.1133M. doi:10.1086/508530.Parameter |coauthors= yang tidak diketahui mengabaikan (|author= yang disarankan) (bantuan)
Freedman, Wendy L.; Madore, Barry F. "The Hubble Constant", Annual Review of Astronomy and Astrophysics, 2010