Patrick Bosc, Olivier Pivert, Amine Mokhtari, Ludovic Lietard. Extending relational algebra to handle bipolarity. In Sung Y. Shin, Sascha Ossowski, Michael Schumacher, Mathew J. Palakal, Chih-Cheng Hung, editors, Proceedings of the 2010 ACM Symposium on Applied Computing (SAC), Sierre, Switzerland, March 22-26, 2010. pages 1718-1722, ACM, 2010. [doi]
@inproceedings{BoscPML10,
  title = {Extending relational algebra to handle bipolarity},
  author = {Patrick Bosc and Olivier Pivert and Amine Mokhtari and Ludovic Lietard},
  year = {2010},
  doi = {10.1145/1774088.1774456},
  url = {http://doi.acm.org/10.1145/1774088.1774456},
  tags = {relational algebra,  algebra},
  researchr = {https://researchr.org/publication/BoscPML10},
  cites = {0},
  citedby = {0},
  pages = {1718-1722},
  booktitle = {Proceedings of the 2010 ACM Symposium on Applied Computing (SAC), Sierre, Switzerland, March 22-26, 2010},
  editor = {Sung Y. Shin and Sascha Ossowski and Michael Schumacher and Mathew J. Palakal and Chih-Cheng Hung},
  publisher = {ACM},
  isbn = {978-1-60558-639-7},
}