@unpublished{cwh,
  title = "Categories for the Working Haskeller",
  author = "Jeremy Gibbons",
  year = "2014",
  howpublished = "Talk at Skills Matter Haskell eXchange",
  month = "September",
  url = "http://www.cs.ox.ac.uk/jeremy.gibbons/publications/cwh-slides.pdf",
}