APA

Johnson D. S., Association for Computing Machinery & ACM Special Interest Group on Algorithms and Computation Theory. (1989). Proceedings of the twenty-first annual ACM symposium on Theory of computing. New York, NY: ACM.

Chicago

Johnson D S, Association for Computing Machinery and ACM Special Interest Group on Algorithms and Computation Theory. 1989. Proceedings of the twenty-first annual ACM symposium on Theory of computing. New York, NY: ACM.

Harvard

Johnson D. S., Association for Computing Machinery and ACM Special Interest Group on Algorithms and Computation Theory. (1989). Proceedings of the twenty-first annual ACM symposium on Theory of computing. New York, NY: ACM.

MLA

Johnson D S, Association for Computing Machinery and ACM Special Interest Group on Algorithms and Computation Theory. Proceedings of the twenty-first annual ACM symposium on Theory of computing. New York, NY: ACM. 1989.