@book {Friedreich1860,
	title = {Geschichte des R{\"a}thsels},
	year = {1860},
	publisher = {Rudolf Kunze},
	organization = {Rudolf Kunze},
	address = {Dresden},
	url = {http://www.janko.at/Raetsel/Gedichte/Friedreich.htm},
	author = {Friedreich, Johannes Baptista}
}
