Kahlert, Johnny, Aivar Leito, Bjarke Laubek, Leho Luigujõe, Andres Kuresoo, Kim Aaen, och Aarne Luud. 2012. ”Factors Affecting the Flight Altitude of Migrating Waterbirds in Western Estonia”. Ornis Fennica 89 (4):241–253. https://doi.org/10.51812/of.133812.