Abell, George O. (1958). “The distribution of rich clusters of galaxies. A catalog of 2712 rich clusters found on the National Geographic Society Palomar Observatory Sky Survey”. 《The Astrophysical Journal Supplement Series》 3: 211–88. Bibcode:1958ApJS....3..211A. doi:10.1086/190036.
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Abell, George O. (1958). “The distribution of rich clusters of galaxies. A catalog of 2712 rich clusters found on the National Geographic Society Palomar Observatory Sky Survey”. 《The Astrophysical Journal Supplement Series》 3: 211–88. Bibcode:1958ApJS....3..211A. doi:10.1086/190036.