@PhdThesis{debois07thesis,
  author = 	 {S{\o}ren Debois},
  title = 	 {Sortings and Bigraphs},
  school = 	 {IT University of Copenhagen},
  year = 	 2008,
  note = 	 {\url{http://www.itu.dk/people/debois/pubs/thesis.pdf}}
}