@inproceedings{DBLP:conf/tapsoft/Hoare89,
  title = "The Varieties of Programming Language",
  author = "C. A. R. Hoare",
  year = "1989",
  booktitle = "TAPSOFT'89: Proceedings of the International Joint Conference on Theory and Practice of Software Development, Barcelona, Spain, March 13-17, 1989, Volume 1: Advanced Seminar on Foundations of Innovative Software Development I and Colloquium on Trees in Algebra and Programming (CAAP'89)",
  editor = "Josep D\'{\i}az and Fernando Orejas",
  pages = "1-18",
  publisher = "Springer",
  series = "Lecture Notes in Computer Science",
  volume = "351",
  doi = "10.1007/3-540-50939-9_121",
}