@book {9783781553958, 
	title = "Kostenfreie Online-Lehrmittel",
	isbn = "9783781553958",
	edition = "1",
	url = "http://www.content-select.com/index.php?id=bib_view&ean=9783781553958",
	url = "https://content-select.com/de/portal/media/view/55102368-5b10-4aab-b803-0f44b0dd2d03",
	publisher = "Verlag Julius Klinkhardt",
}