Dreyer, « Second Index Catalogue of Nebulae and Clusters of Stars; Containing Objects Found in the Years 1895 to 1907, with Notes and Corrections to the New General Catalogue and to the Index Catalogue for 1888–94 », Memoirs of the Royal Astronomical Society, vol. 59, , p. 105–198 (Bibcode1910MmRAS..59..105D, lire en ligne)
Dreyer, « Second Index Catalogue of Nebulae and Clusters of Stars; Containing Objects Found in the Years 1895 to 1907, with Notes and Corrections to the New General Catalogue and to the Index Catalogue for 1888–94 », Memoirs of the Royal Astronomical Society, vol. 59, , p. 105–198 (Bibcode1910MmRAS..59..105D, lire en ligne)