@InProceedings{alti:icalp04,
  author = 	 {Michael Abbott and Thorsten Altenkirch and Neil Ghani},
  title = 	 {Representing Nested Inductive Types using {W-types}},
  booktitle = 	 {Automata, Languages and Programming, 31st International Colloqium (ICALP)},
  pages =	 {59 -- 71},
  year =	 {2004}
}