nl_tokens: Filters word combinations beginning and ending with certain function words .
pl_tokens: function filterFunctionWordsAtBeginningAndEnding ( wordCombinations , functionWords ) { wordCombinations = filterFunctionWordsAtBeginning ( wordCombinations , functionWords ) ; wordCombinations = filterFunctionWordsAtEnding ( wordCombinations , functionWords ) ; <mask> wordCombinations ; }