How do you footnote a footnote!?

This is a special case:





I'm trying to cite a footnote from an essay in a collection. But I'm not citing it in the body of my text, rather in a footnote of my own. So the question is-- how do you footnote a footnote, within a footnote? (Is that even proper style? I've thought about trying to do this in other ways, but it really only works in the form I'm just described).How do you footnote a footnote!?
wow, thats a good one. hardest question ever.

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