\documentclass[a4paper,10pt]{article}
\usepackage[utf8]{inputenc}
\title{Bibliography management: BibTeX}
\author{Share\LaTeX}
\begin{document}
\maketitle
This document is an example of BibTeX using in bibliography management. Three items are cited: \textit{The \LaTeX\ Companion} book \cite{latexcompanion}, the Einstein journal paper \cite{einstein}, and the Donald Knuth's website \cite{knuthwebsite}. The \LaTeX\ related items are \cite{latexcompanion,knuthwebsite}.
\medskip
\bibliographystyle{unsrt}%Used BibTeX style is unsrt
\bibliography{sample}
\end{document}