Kalejta-Summers, Bozena, and David Butterfield. “Numbers and Distribution of Wintering Divers, Grebes and Seaducks in the Moray Firth, Scotland, 1998 99-2003 04”. Wildfowl, Apr. 2013, pp. 113-28, https://tidsskrift.dk/Wildfowl/article/view/153967.