Replace `et al.` in a citation with all authors surnames of the reference

Question

In the book MWE used in this question, I'm using the natbib package to generate the bibliography with the abbrvnat style described in this page. I would like to have the citation of a reference with three authors to include all of their surnames, instead of the first author's surname followed by et al..

The command \citet*{Byrd:19} does include all three authors of the particular reference Byrd:19, but I need to have everything inside the brackets. Please see the figure below.

The example reference entries, included in a separate bibtex file—reference.bib, are:

@article{Byrd:19,
    author = {Byrd, Richard~H. and Cocola, Jorio and Tapia, Richard~A.},
    title = {{Extending the Pennisi--McCormick Second-Order Sufficiency Theory for Nonlinear Programming to Infinite Dimensions}},
    journal = {SIAM Journal on Optimization},
    year = {2019},
    volume = {29},
    number = {3},
    pages = {1870-1878}}

Thanks for any idea you could provide.

Answer 1

Assuming you're still using the abbrvnat bibliography style, I suggest you (a) load the natbib package with the options square and authoryear and (b) use \citep* instead of \citet* to create "parenthetic-style" citation call-outs that show all authors' surnames. Conversely, use \citep to create parenthetic-style citation call-outs with truncated author lists for entries with three or more authors or editors.

\documentclass{extreport}
\begin{filecontents}[overwrite]{references.bib}
@article{Byrd:19,
    author = {Byrd, Richard H. and Cocola, Jorio and Tapia, Richard A.},
    title  = {Extending the {Pennisi--McCormick} Second-Order Sufficiency 
             Theory for Nonlinear Programming to Infinite Dimensions},
    journal= {SIAM Journal on Optimization},
    year   = {2019},
    volume = {29},
    number = {3},
    pages  = {1870-1878},
}
\end{filecontents}
\usepackage[square,authoryear]{natbib} 
\bibliographystyle{abbrvnat} % or some other suitable bib style
\begin{document}
\citep*{Byrd:19}, \citep{Byrd:19}
\bibliography{references}
\end{document}