van der Wal, Reinder J., and Piet J Zomerdijk. “The Moulting of Tufted Duck and Pochard on the IJsselmeer in Relation to Moult Concentrations in Europe”. Wildfowl (January 1, 1979): 99–108. Accessed December 18, 2025. https://tidsskrift.dk/Wildfowl/article/view/154135.