BOIKO, Dmitrijs; KAMPE-PERSSON, Hakon. Breeding Whooper Swans Cygnus cygnus in Latvia, 1973-2009. Wildfowl, [S. l.], p. 168–177, 2013. Disponível em: https://tidsskrift.dk/Wildfowl/article/view/153535. Acesso em: 16 dec. 2025.