ReijndersP. J., BrasseurS. M., TougaardS., SeibertU., BorchardtT., and StedeM. “Population Development and Status of Harbour Seals (<i>Phoca vitulina</I&gt;) in the Wadden Sea”. NAMMCO Scientific Publications, Vol. 8, Sept. 2010, pp. 95-105, doi:10.7557/3.2677.