@incollection{Bender06,
  author = {Bender, Emily M.},
  title = {Variation and Formal Theories of Language: HPSG},
  booktitle = {Encyclopedia of Language and Linguistics},
  edition = {2nd},
  volume = {13},
  pages = {326--329},
  editor = {Brown, Keith},
  publisher = {Elsevier},
  address = {Oxford},
  year = {2006}
}