when uploading articles written in LaTeX to arxiv, because the file .bib cannot be used as a reference, this is very troublesome, mainly because the macro package \usepackage{natbib} will report an error. With the help of overleaf, the solution is to first download and package everything you need for the entire LaTeX compilation, preferably compiled locally, and then replace the content in .tex with the reference section in .tex

	%\bibliographystyle{unsrt}
	%\bibliography{refs}

is actually ok locally, but not on arxiv. The following steps are required:
. Comment out \usepackage{natbib}
2. Comment out the following part of the .sty file :

% load natbib unless told otherwise
% \if@natbib
%   \RequirePackage{natbib}
% \fi

then compiles on arxiv.