@inproceedings{Gibbons95:Initial,
  title = "An Initial-Algebra Approach to Directed Acyclic Graphs",
  author = "Jeremy Gibbons",
  year = "1995",
  booktitle = "Mathematics of Program Construction",
  editor = "Bernhard M{\"o}ller",
  pages = "282--303",
  publisher = "Springer-Verlag",
  series = "Lecture Notes in Computer Science",
  url = "http://www.cs.ox.ac.uk/people/jeremy.gibbons/publications/damgs.ps.gz",
  volume = "947",
}