↑R. W. Sinnott, editor (1988). The Complete New General Catalogue and Index Catalogue of Nebulae and Star Clusters by J. L. E. Dreyer. Sky Publishing Corporation and Cambridge University Press. ISBN0-933-34651-4. {{cite book}}: |author= has generic name (help)
↑Q. Daniel Wang et al., [http://arxiv.org/abs/astro-ph/0308150v1 Chandra Observation of the Edge-on Galaxy NGC 3556 (M 108):
Violent Galactic Disk-halo Interaction Revealed]
↑Kepple, George Robert (1998). The Night Sky Observer's Guide, Volume 2. Willmann-Bell, Inc. p. 399. ISBN0-943396-60-3. {{cite book}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)