@INPROCEEDINGS{mp04B,
  author = {A. Montanari and G. Puppis},
  title = {Decidability of {M}{S}{O} Theories of Tree Structures},
  booktitle = {Proceedings of the 24th Conference on Foundations of Software Technology
 and Theoretical Computer Science (FSTTCS)},
  year = {2004},
  volume = {3328},
  series = {LNCS},
  pages = {430-442},
  publisher = {Springer}
}