@book{21980,
	author = {Witkam, W.G.M., and Velema, W.H.},
	title = {Reageerbuisbevruchting verantwoord? /},
	publisher = {Buijten & Schipperheijn,},
	year = {cop. 1990.},
	series = {Lindeboomreeks ;},
	address = {Amsterdam :}
}