@book{7100,
	author = {Janssen, B. H. and Wienk, J. F.},
	title = {Mechanized annual cropping on low fertility acid soils in the humid tropics; a case study of the Zanderij soils in Suriname},
	publisher = {Agricultural University,},
	year = {1990},
	series = {Wageningen Agricultural University Papers},
	address = {Wageningen :}
}