\begin{thebibliography}{widest-label}
\bibitem[label]{cite_key}
literature citation ...
....
\end{thebibliography}
The thebibliography environment produces a bibliography or reference
list. In the article style, this reference list is labeled
"References"; in the report style, it is labeled "Bibliography".
widest-label is text that, when printed, is approximately as wide as the widest item label produced by the \bibitem command.
The thebibliography environment is similar to the enumerate environment, except that items are associated with a \bibitem command and can be cross-referenced with the \cite command.
... In the running text you might want to refer to
Dow & Jones\cite{DandJ} and then again you
might not ...
The \cite
command will produce a sequence number by default,
or the text from the optional label argument of
\bibcite; this latter is useful
if the style is to use, for example,
the first three letters of the author's last name and a year, as in Dow29.
The associated item in the bibliography section at the end of the article would be generated by
\begin{thebibliography}{99}
....
\bibitem{DandJ} Dow, W. \& Jones, E.A.,
{\it Wall Street Journal},
March 29, 1929.
....
\end{thebibliography}
Note that the widest-label parameter has been set assuming less than
100 numbered items in the bibliography. Also note that the key,
DandJ, is what connects the \cite
and \bibitem.
If label is omitted, the numbers are generated sequentially by the \bibitem commands. Many journals want these in order of appearance in the text, so you have to sort this list to the proper order.