Korner-Nievergelt, Fränzi R, Josef Hofer, Annette Sauter, and Lukas Jenni. 2009. “Measuring Within-Winter Movement Rates of Tufted Duck Aythya Fuligula and Common Pochard A. Ferina Based on Ring Re-Encounter Data”. Wildfowl, May, 24-41. https://tidsskrift.dk/Wildfowl/article/view/153583.