@article {Drent1998,
	title = {Barnacle geese Branta leucopsis on Nordenski{\"o}ldkysten, western Spitsbergen-in thirty years from colonisation to saturation},
	journal = {Norsk Polarinstitutt Skrifter},
	year = {1998},
	url = {http://www.maartenloonen.nl/literatuur/nps200-105-drent.pdf},
	author = {Drent, RH and Black, JM}
}
