Baldwin, J. A.; Wampler, E. Joseph; Gaskell, C. Martin (1989). "Emission-line properties of optically and radio-selected complete quasar samples". Astrophysical Journal, Part 1. 338: 630–653. Bibcode:1989ApJ...338..630B. doi:10.1086/167224. ISSN0004-637X.
Baldwin, J. A.; Wampler, E. Joseph; Gaskell, C. Martin (1989). "Emission-line properties of optically and radio-selected complete quasar samples". Astrophysical Journal, Part 1. 338: 630–653. Bibcode:1989ApJ...338..630B. doi:10.1086/167224. ISSN0004-637X.
Baldwin, J. A.; Wampler, E. Joseph; Gaskell, C. Martin (1989). "Emission-line properties of optically and radio-selected complete quasar samples". Astrophysical Journal, Part 1. 338: 630–653. Bibcode:1989ApJ...338..630B. doi:10.1086/167224. ISSN0004-637X.