@book{136,
	author = {Lewis, Harry R. and Papadimitriou, Christos H.,},
	title = {Elements of the theory of computation /},
	publisher = {Prentice-Hall,},
	year = {c1981.},
	series = {Prentice-Hall software series},
	address = {Englewood Cliffs, N.J. :},
	edition = {2nd ed.}
}