R. E. White, III, W. C. Keel, C. J. Conselice (2000). “Seeing Galaxies through Thick and Thin. I. Optical Opacity Measures in Overlapping Galaxies”. Astrophysical Journal542 (2): 761-778. Bibcode: 2000ApJ...542..761W. doi:10.1086/317011.
R. E. White, III, W. C. Keel, C. J. Conselice (2000). “Seeing Galaxies through Thick and Thin. I. Optical Opacity Measures in Overlapping Galaxies”. Astrophysical Journal542 (2): 761-778. Bibcode: 2000ApJ...542..761W. doi:10.1086/317011.