George S. Lueker, Edward L. Robertson. That really is a hard problem you've spent six months working on: A tutorial on NP-complete problems. In Toni Shelter, Steven Abraham, Emily P. Friedman, Beth Levy, editors, Proceedings of the ACM 1981 Annual Conference, Los Angeles, CA, USA, November 9-11, 1981. pages 293-294, ACM, 1981. [doi]
Abstract is missing.