@article{journals/ipl/CeriGTW89,
  title = "Magic Semi-Joins",
  author = "Stefano Ceri and Georg Gottlob and Letizia Tanca and Gio Wiederhold",
  year = "1989",
  journal = "Inf. Process. Lett.",
  number = "2",
  pages = "97-107",
  volume = "33",
}