Gudmundsson, Finnur, Pekka Grenquist, Kai Curry-Lindhal, Knud Paludan, Holger Holgersen, Erik Kumari, M F Mrzer Bruijns, et al. 1961. “Wildfowl Research and Conservation in Europe in 1961”. Wildfowl, January, 28. https://tidsskrift.dk/Wildfowl/article/view/155812.