Lok, Martin, Leo van den Berg, Barwolt Ebbinge, Anton van Haperen, Jules Philippona, Jouke Prop, and Arend Timmerman Azn. 1992. “Numbers and Distribution of Wild Geese in the Netherlands, 1984-89, With Special Reference to Weather Conditions”. Wildfowl, January, 107-16. https://tidsskrift.dk/Wildfowl/article/view/155365.