Thanks, there isn't supposed to be one - the reference was a leftover from an earlier draft. Deleted it.

(I originally had a separate footnote mentioning that the "argument from ignorance" discussion in this post only discusses the "negative evidence" aspect, with there also existing two other aspects (epistemic closure and shifting the burden of proof) that can be found in the original paper. But then I compressed the footnote into just the "For math, experimental studies, and two other subtypes of the argument from ignorance..." sentence in the current version.)