Quellenangaben

• [331] «Globular Clusters and Planetary Nebulae Discovered on the National Geographic Society-Palomar Observatory Sky Survey» Abell, G. O.; Publications of the Astronomical Society of the Pacific, Vol. 67, No. 397, p.258-261, August 1955; DOI:10.1086/126815; Bibcode:1955PASP...67..258A
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