Bregnballe, T., Schjørring, S. E., Gregersen, J., Abrahamsen, L., Fritze, E. & Baccetti, N. (Ed.) (1997).
Plastic Leg-Ring Wear and Loss in a Study of Cormorants.
Supplementi alle Ricerche di Biologia della Selvaggina,
26, 377-382.
Fox, A. D., Stawarczyk, T., Hagemeijer, W. J. M. (Ed.) & Blair, M. J. (Ed.) (1997).
Pochard Aythya ferina. In W. J. M. Hagemeijer & M. J. Blair (Eds.),
The EBCC Atlas of European Birds: their Distribution and Abundance (pp. 102-103). Poyser.