Noer, H., Laursen, K., Pihl, S., Hansen, M. & Madsen, J. (Ed.) (1993).
Interspecific winter distribution of diving ducks and other waterfowl in Danish waters. In J. Madsen (Ed.),
Proceedings of the Seventh Nordic Congress of Ornithology, 1990 (pp. 26-30). National Environmental Research Institute.