The fn-group usually contains footnotes corresponding to the article.
However, since footnotes are currently not fully supported by DfR,
there is no comprehensive documentation on the different variants. jstor
therefore extracts the content of fn-group exactly as it appears in the
data. Because of this, there might be other content present than footnotes.
In order to get all available information on citation data, you might need to
combine jst_get_footnotes() with jst_get_references().