SOVON (1987) Cooperating Organizations Vogelonderzoek Netherlands. Point-transect counts, SOVON a project for winter birds. LIMOSA 60 (2): 95-95.

In the autumn of 1978 began fieldwork Atlas Project for the Winter and migratory birds. That same winter was half SOVON project started, the point-transect-counts (PTT) project for winter birds. The Atlas Project was to outset based on a large crowd of people.

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