Kahlert, J., A. Leito, B. Laubek, L. Luigujõe, A. Kuresoo, K. Aaen, and A. Luud. “Factors Affecting the Flight Altitude of Migrating Waterbirds in Western Estonia”. Ornis Fennica, vol. 89, no. 4, Dec. 2012, pp. 241–253, doi:10.51812/of.133812.