@Unpublished{     collins:PCFG,
  Author        = "Collins, Michael",
  date-added    = "2019-07-09 07:39:01 +0200",
  date-modified = "2019-07-09 07:39:38 +0200",
  Keywords      = "probabilistic context-free grammars",
  Title         = "Probabilistic Context-Free Grammars (PCFGs)",
  File          = "pcfgs (0) - a - a - v.pdf"
}

@Unpublished{ collins:PCFG, Author = "Collins, Michael", date-added = "2019-07-09 07:39:01 +0200", date-modified = "2019-07-09 07:39:38 +0200", Keywords = "probabilistic context-free grammars", Title = "Probabilistic Context-Free Grammars (PCFGs)", File = "pcfgs (0) - a - a - v.pdf" }