@article{simon11two,
  author = {A. Simon and A. King and J. Howe},
  title = {The {T}wo {V}ariable {P}er {I}nequality {A}bstract {D}omain},
  journal = {Higher Order and Symbolic Computation},
  year = 2011,
  publisher = {Springer},
  doi = {10.1007/s10990-010-9062-8},
}