Brahim Hnich Toby Walsh Barbara M. Smith Dual Modelling of Permutation and Injection Problems. 357-391 2004 21 J. Artif. Intell. Res. (JAIR) http://www.cs.washington.edu/research/jair/abstracts/hnich04a.html db/journals/jair/jair21.html#HnichWS04