is.name <- function(bigram){
    has.last.name <- tolower(bigram[2]) %in% tolower(last.names$name)
    if(has.last.name){      
      has.first.name <- tolower(bigram[1]) %in% tolower(first.names)
      isname <- has.first.name & has.last.name
    }else{
      isname <- has.last.name
    }
    return(isname)
  }