@book{12099,
	author = {Garey, Michael R. and Johnson, David S. and Johnson, David S. ; jt. auth.},
	title = {Computers and intractability; a guide to the theory of NP-Completeness},
	publisher = {W. H. Freeman},
	year = {1979},
	series = {Mathematical Sciences},
	address = {San Francisco}
}