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]
@inproceedings{LuekerR81,
title = {That really is a hard problem you've spent six months working on: A tutorial on NP-complete problems},
author = {George S. Lueker and Edward L. Robertson},
year = {1981},
doi = {10.1145/800175.809904},
url = {http://doi.acm.org/10.1145/800175.809904},
researchr = {https://researchr.org/publication/LuekerR81},
cites = {0},
citedby = {0},
pages = {293-294},
booktitle = {Proceedings of the ACM 1981 Annual Conference, Los Angeles, CA, USA, November 9-11, 1981},
editor = {Toni Shelter and Steven Abraham and Emily P. Friedman and Beth Levy},
publisher = {ACM},
isbn = {0-89791-049-4},
}