PATTERSON, I J; YOUNG, C M; TOMPA, F S. The Shelduck population of the Ythan estuary, Aberdeenshire. Wildfowl, [S. l.], p. 16–28, 1974. Disponível em: https://tidsskrift.dk/Wildfowl/article/view/155879. Acesso em: 18 dec. 2025.