@book{6781,
	author = {Gratzer, George A.},
	title = {Universal algebra /},
	publisher = {Springer-Verlag,},
	year = {c1979.},
	address = {New York :},
	edition = {2d ed.},
	note = {Includes index.},
	url = {http://www.loc.gov/catdir/enhancements/fy1005/78012113-d.html}
}