@Article{subg,
  AUTHOR         = {Vlado Keselj and Nick Cercone},
  TITLE          = {A Formal Approach to Subgrammar Extraction for NLP},
  JOURNAL        = {Mathematical and Computer Modelling},
  VOLUME         = { 45},
  PAGES          = { 394--403},
  YEAR           = {  2007},
  MONTH          = { February},
}