VOOUS KH (1959) Literatuur: V. Olssen. 1958. Dispersal, migration, longevity and death causes of Strix aluco, Buteo buteo, Ardea cinera and Larus argentatus. LIMOSA 32 (3): 180-180.

Viking OLSSON: Dispersal, migration, longevity and death causes at Strix aluca, Buteo buteo, Ardea cinerea and Lams argentatus. Acta Vertebratica I (2), 1958, pp. 85

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