@article{Seidl92Single-Valuedness,
  author = {Helmut Seidl},
  title = {Single-{V}aluedness of {T}ree {T}ransducers is {D}ecidable in {P}olynomial {T}ime},
  journal = {Theor. Comput. Sci.},
  year = 1992,
  pages = {135-181},
  volume = {106},
  number = {1},
}