Kampe-Persson, Hakon, Dmitrijs Boiko, and Julius Morkūnas. 2012. “Distribution and Numbers of Moulting Non-Breeding Whooper Swans Cygnus Cygnus in the Baltic States and South Sweden”. Ornis Svecica 22 (3–4). Lund, Sweden:127–138. https://doi.org/10.34080/os.v22.22588.