GreenFile has other ways to filter results once a search has been performed. Users can find these filtering options on the left side of the screen under "Refine Results."

Some of the options are the same as those listed under the "Search Options" tab, like limiting the publication date range, or returning results which include peer-reviewed materials only. 

Additional options for filtering include things like subject type, which can limit to individual search terms, or expand to include related search terms. In this case, additional search terms like "air pollutants" and "environmental exposure are also available. Using the filter options presented with the search results also allows users to limit results by language, and even the geographic focus of the article.