Irion, R. (2001). Galaxies: Island universes. Reader's Digest.
Tohutoru Kātū Chicago (17th ed.)Irion, Robert. Galaxies: Island Universes. Pleasantville: Reader's Digest, 2001.
Tohutoro MLA (9th ed.)Irion, Robert. Galaxies: Island Universes. Reader's Digest, 2001.
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