COLLINDER, Per. On Structural Properties of Open Galactic Clusters and their Spatial Distribution. Catalog of Open Galactic Clusters. S. B1-B46. Annals of the Observatory of Lund [online]. 1931 [cit. 2019-12-16]. Čís. 2, s. B1-B46. Dostupné online. Bibcode1931AnLun...2....1C. (anglicky)
COLLINDER, Per. On Structural Properties of Open Galactic Clusters and their Spatial Distribution. Catalog of Open Galactic Clusters. S. B1-B46. Annals of the Observatory of Lund [online]. 1931 [cit. 2019-12-16]. Čís. 2, s. B1-B46. Dostupné online. Bibcode1931AnLun...2....1C. (anglicky)