J. C. Franson, T. Hollmén, M, M. Hario, M. Kilpi, and D. L. Finley, “Lead and delta-aminolevulinic acid dehydratase in blood of Common Eiders (Somateria mollissima) from the Finnish archipelago”, Ornis Fenn, vol. 79, no. 2, pp. 87–91, Jul. 2002.