Irion, R. (2001). Galaxies: Island universes. Reader's Digest.
Chicago-čujuhus (17. p.)Irion, Robert. Galaxies: Island Universes. Pleasantville: Reader's Digest, 2001.
MLA-čujuhus (9. p.)Irion, Robert. Galaxies: Island Universes. Reader's Digest, 2001.
Muitte dárkkistit čujuhemiid riektatvuođa, ovdal go geavahat daid iežat deavsttas.