NILSSON, Leif. Long-term trends in the number of Whooper Swans Cygnus cygnus breeding and wintering in Sweden. Wildfowl, [S. l.], p. 197–206, 2014. Disponível em: https://tidsskrift.dk/Wildfowl/article/view/153624. Acesso em: 16 dec. 2025.