Laura Magrini, Letizia Stanghellini, Eva Villaver. The Planetary Nebula Population of M33 and its Metallicity Gradient: A Look Into the Galaxy's Distant Past. „The Astrophysical Journal”. 696 (1), s. 729–740, Maj 2009. DOI: 10.1088/0004-637X/696/1/729. arXiv:0901.2273. Bibcode: 2009ApJ...696..729M.
Bonanos A. Z., Stanek K. Z., Kudritzki R. P., Macri L., Sasselov D. D., Kaluzny J., Bersier D., Bresolin F., Matheson T., Mochejska B. J., Przybilla N., Szentgyorgyi A. H., Tonry J., Torres G.. The First DIRECT Distance to a Detached Eclipsing Binary in M33. „Astrophysics and Space Science”. 304 (1–4), s. 207–209, 2006. DOI: 10.1007/s10509-006-9112-1. Bibcode: 2006Ap&SS.304..207B.
Laura Magrini, Letizia Stanghellini, Eva Villaver. The Planetary Nebula Population of M33 and its Metallicity Gradient: A Look Into the Galaxy's Distant Past. „The Astrophysical Journal”. 696 (1), s. 729–740, Maj 2009. DOI: 10.1088/0004-637X/696/1/729. arXiv:0901.2273. Bibcode: 2009ApJ...696..729M.
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Bonanos A. Z., Stanek K. Z., Kudritzki R. P., Macri L., Sasselov D. D., Kaluzny J., Bersier D., Bresolin F., Matheson T., Mochejska B. J., Przybilla N., Szentgyorgyi A. H., Tonry J., Torres G.. The First DIRECT Distance to a Detached Eclipsing Binary in M33. „Astrophysics and Space Science”. 304 (1–4), s. 207–209, 2006. DOI: 10.1007/s10509-006-9112-1. Bibcode: 2006Ap&SS.304..207B.
Laura Magrini, Letizia Stanghellini, Eva Villaver. The Planetary Nebula Population of M33 and its Metallicity Gradient: A Look Into the Galaxy's Distant Past. „The Astrophysical Journal”. 696 (1), s. 729–740, Maj 2009. DOI: 10.1088/0004-637X/696/1/729. arXiv:0901.2273. Bibcode: 2009ApJ...696..729M.