found: Work cat.: Keane, S.E. Effects of herring gulls and great black-backed gulls on breeding piping plovers, South Monomoy Island, Massachusetts, 2002:PDF p. 1 (Great-black Backed Gull (Larus argentatus [sic]) and Herring Gull (L. marinus [sic]))
found: ITIS, Apr. 7, 2005(Larus marinus Linnaeus, 1758 -- valid -- great black-backed gull)
found: NatureServe explorer, via WWW, Apr. 7, 2005(Larus marinus, Great Black-backed Gull)
found: eNature Online field guides, Apr. 7, 2005(Great Black-backed Gull, Larus marinus)
found: The A.O.U. check-list of North American birds, via WWW, Apr. 7, 2005(Larus marinus, Great Black-backed Gull)
found: Annotated list of the seabirds of the world, via WWW, Apr. 7, 2005(Larus marinus, Great Black-backed Gull)
found: Avibase, via WWW, Apr. 7, 2005(Great Black-backed Gull (Larus marinus). Other names: Great-Black-backed Gull, Greater Black-backed Gull)