Columbia subject headings:
Harvard subject headings:
Birds--Ecology--Netherlands--Waddenzee--Congresses.
Nature conservation--Netherlands--Waddenzee--Congresses.
Waddenzee (Netherlands)--Congresses.
Water birds--Netherlands--Waddenzee--Congresses.
Princeton subject headings:
Birds--Netherlands--Waddenzee--Congresses.
Ecology--Netherlands--Waddenzee--Congresses.
Nature conservation--Netherlands--Waddenzee--Congresses.
Waddenzee (Netherlands)--Congresses.