How to change citation call-outs from authoryear-style to numeric-style?

Question

I am using this template

https://www.overleaf.com/project/new/template/29119?id=28568212&latexEngine=pdflatex&mainFile=cas-dc-template.tex&templateName=Elsevier%E2%80%99s+CAS+LaTeX+Double-Column+Template&texImage=texlive-full%3A2022.1

When I compile this LaTeX document I get citation call-outs in authoryear style, aka Harvard style, like this

But what I want is to have the citation call-outs use numeric style, like this

How can i do that?

here is part of my writing

... which is the American version  \cite{803, 805}.

Answer 1

You need to make two changes.

First, please change

\usepackage[authoryear,longnamesfirst]{natbib}

to

\usepackage[numbers,square,sort&compress]{natbib}

Second, please change

\bibliographystyle{cas-model2-names}

to

\bibliographystyle{elsarticle-num}

of some other suitable bib style.

After applying these changes, it's necessary to run a full recompile cycle -- LaTeX, BibTeX, and LaTeX twice more -- to propagate them to all citation call-outs.