How to do footnoes in AO3:
<a name="foot1t" id="foot1t"></a><a href="#foot1"><small><sup>1</sup></small></a>in the text you want to footnote, and then at the bottom
<a name="foot1" id="foot1"></a><a href="#foot1t"><small><sup>1</sup></small></a>changing the 1s to whatever number footnote you're up to.
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