There are several possibilities. First, Extractor ignores words with less than three letters. You will need access to the source code if you wish to remove words or phrases from the stop word or stop phrase lists. A go phrase will be found, when it appears in the input document, even if it also appears in the stop word or stop phrase lists. In our documents, we have phrases with four and more words.
Extractor is designed to extract key phrases with one, two, or three words.
When we try to include phrases with four or more words, we can cover a few more of the authors' key phrases, but we also introduce a few more errors. Since there is a net loss, Extractor does not attempt to cover these longer phrases. You can then extract, from the highlights, the phrases that are marked in bold, by writing your own routine to process the output highlights. If you are programming in Java, Perl, Python, or Visual Basic, we have some experience with calling Extractor from these languages. Please contact us for help.