Karp, Richard, Reducibility Among Combinatorial Problems(PDF), Miller, R. E.; Thatcher, J. W. (编), Proceedings of a Symposium on the Complexity of Computer Computations, Plenum Press: 85–103, 1972 [2008-08-29], (原始内容(PDF)存档于2011-06-29)
Karp, Richard, Reducibility Among Combinatorial Problems(PDF), Miller, R. E.; Thatcher, J. W. (编), Proceedings of a Symposium on the Complexity of Computer Computations, Plenum Press: 85–103, 1972 [2008-08-29], (原始内容(PDF)存档于2011-06-29)