@inproceedings{conf/pods/KostylevRS12,
  title = "Classification of annotation semirings over query containment",
  author = "Egor V. Kostylev and Juan L. Reutter and Andr{\'{a}}s Z. Salamon",
  year = "2012",
  booktitle = "Proceedings of the 31st {ACM} {SIGMOD-SIGACT-SIGART} Symposium on Principles of Database Systems ({PODS} 2012), Scottsdale, Arizona, USA, May 20-24, 2012",
  pages = "237--248",
  publisher = "{ACM}",
}