# List the bibliography according it appear in the text

I am writing a article for Elsevier, and I would like that the bibliography appear in the section of "references" according the citations are appearing in the text.

For example

I would like that the reference 29 appear like the reference number 1 instead of 29.

I am working with the following preamble

\documentclass[preprint,12pt]{elsarticle}
% !TeX spellcheck = en_US
\usepackage{siunitx}
\sisetup{detect-weight, detect-display-math}
\sisetup{detect-inline-weight=math}
\sisetup{mode=text,per-mode=symbol}
\usepackage{booktabs}
\usepackage{graphicx}
\usepackage{pgfplots}
\usepackage{pdflscape}
\usetikzlibrary{plotmarks}
\usetikzlibrary{arrows.meta}
\usepgfplotslibrary{patchplots}
\newlength\fwidth
\setlength{\fwidth}{0.8\textwidth}
\pgfplotsset{plot coordinates/math parser=false}
\usepackage{overpic}
\pgfplotsset{compat=1.15}
\usepackage{float}
\usepackage{etoolbox}
\bibliographystyle{abbrvnat}
\usepackage{bicaption}
\usepackage{makecell}
\usepackage[skip=1ex, labelfont=bf]{caption}
\usepackage[skip=0.333\baselineskip]{caption}
\usepackage{tabularx}
\newcolumntype{C}{>{\centering\arraybackslash}X}
\def\UrlFont{\normalfont}
\sisetup{per-mode=symbol}
\usepackage[margin=2.5cm]{geometry}
\usepackage[skip=0.333\baselineskip]{caption}
\usepackage{amssymb,amsmath}
\usepackage{url}
\usepackage{hyperref}
\journal{Fuel}
\begin{document}

\section{Introduction}
Oil shales (OS) are fine grain sedimentary rocks that contain organic material of high molecular weight, called kerogen, disseminated in its inorganic matrix [\cite{scouten1990fuel}, \cite{allred1982oil}].

\section*{References}
\bibliography{bilbiography}

%% else use the following coding to input the bibitems directly in the
%% TeX file.

\end{document}

\endinput


The bibliography has 37 references, and I would that each reference appear in the bibliography according it appear in the text.

Could anyone help me?

You need to

• change the argument of \bibliographystyle from abbrvnat (which performs alphabetical sorting by authors' surnames) to unsrtnat (which performs no sorting); then,

• perform a full recompile cycle: LaTeX, BibTeX, and LaTeX twice more.

Here's a screenshot of a simplified version of your MWE (minimum working example); observe that the Scouten entry, which is cited first, is numbered 1, whereas the Allred entry is numbered 2. Correspondingly, the Scouten entry is listed before the Allred bibliography in the references.

In the following, I've also tried to clean up, simplify, and organize the preamble code.

\RequirePackage{filecontents}
%% create a dummy bib file
\begin{filecontents}{bilbiography.bib}
@misc{allred1982oil,
author = "Allred",
title  = "Oil",
year   = 1982,
}
@misc{scouten1990fuel,
author = "Scouten",
title  = "Fuel",
year   = 1990,
}
\end{filecontents}

\documentclass[preprint,12pt]{elsarticle}
\journal{Fuel}
\bibliographystyle{unsrtnat} % not 'abbrvnat'

\usepackage[margin=2.5cm]{geometry}
\usepackage{amssymb,amsmath,booktabs,
graphicx,pdflscape,float}
\usepackage{etoolbox} % do you need this package?
\usepackage{bicaption}% ditto

\usepackage{siunitx}
\sisetup{detect-weight,
detect-display-math,
detect-inline-weight=math,
mode=text,
per-mode=symbol}

\usepackage{pgfplots,overpic}
\usetikzlibrary{plotmarks}
\usetikzlibrary{arrows.meta}
\usepgfplotslibrary{patchplots}
\newlength\fwidth
\setlength{\fwidth}{0.8\textwidth}
\pgfplotsset{plot coordinates/math parser=false}
\pgfplotsset{compat=1.15} % conflict with 'compat=newest' (see above)!

\usepackage{makecell}

\usepackage{caption}
\captionsetup{labelfont=bf,skip=0.333\baselineskip}

\usepackage{tabularx}
\newcolumntype{C}{>{\centering\arraybackslash}X}

\usepackage[hyphens,spaces,obeyspaces]{url}
\def\UrlFont{\normalfont}