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\begin{filecontents}{mybib.bib}
@article{ref1,
    author    = {Guyon, Isabelle and Elisseeff, Andr\'{e}},
    journal   = {The Journal of Machine Learning Research},
    pages     = {1157--1182},
    title     = {{An introduction to variable and feature selection}},
    volume    = {3},
    year      = {2003}
}
@book{ref2,
    author    = {Michel Goossens and Frank Mittelbach and Alexander Samarin},
    title     = {The LaTeX Companion},
    year      = {1993},
    publisher = {Addison-Wesley},
    address   = {Reading, Massachusetts}
}
\end{filecontents}

\addbibresource{mybib.bib}

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\begin{document}
Lorem ipsum dolor sit amet \parencite{ref1}, consectetur adipiscing elit \parencite{ref2}.

\printbibliography
\end{document}