@article{EngelfrietMS09Deciding,
  author = {Joost Engelfriet and Sebastian Maneth and Helmut Seidl},
  title = {Deciding equivalence of top-down {XML} transformations in polynomial time},
  journal = {J. Comput. Syst. Sci.},
  year = 2009,
  pages = {271--286},
  volume = {75},
  number = {5},
  doi = {10.1016/j.jcss.2009.01.001},
}