Another aspect to warn against is the complete lack of markup quality control in arXiv, which inevitably leads to a variety of errors that add ”noise” to the dataset. As the range of structures in LaTeXis broader than plaintext, these errors are also more diverse. Examples are:

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  Regular plaintext typos

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  Inconsistent use of unicode characters in names (e.g. ”Poincare” vs ”Poincaré”)

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  Mathematical expressions left in text mode, as well as textual expressions added as formulas for stylistic convenience(such as 1$^{st}$ or using $\bullet$ to denote an \item ).

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  Citations and references are inconsistently automated (via \ref and \cite ), while sometimes left in as explicit numbers.

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  An old but quite detailed rough list of such issues can be found here, and probably needs to be revived in a separate document.