@book{16144,
	author = {Galen, Frans van, and Feijs, Els,},
	title = {Fractions, Percentages, Decimals and Proportions :},
	publisher = {Brill | Sense,},
	year = {2008.},
	series = {Dutch Design in Mathematics Education ;},
	address = {Leiden; },
	url = {http://dx.doi.org/10.1163/9789460911422}
}