DREYER, J. L. E. A New General Catalogue of Nebulæ and Clusters of Stars, being the Catalogue of the late Sir John F. W. Herschel, Bart, revised, corrected, and enlarged. S. 237. Memoirs of the Royal Astronomical Society [online]. 1888 [cit. 2019-11-29]. Roč. 49, s. 237. Dostupné online. Bibcode1888MmRAS..49....1D. (anglicky)
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DREYER, J. L. E. A New General Catalogue of Nebulæ and Clusters of Stars, being the Catalogue of the late Sir John F. W. Herschel, Bart, revised, corrected, and enlarged. S. 237. Memoirs of the Royal Astronomical Society [online]. 1888 [cit. 2019-11-29]. Roč. 49, s. 237. Dostupné online. Bibcode1888MmRAS..49....1D. (anglicky)