adding your own reference bib to latex code example

Example 1: latex use biblatex

% In the preamble you need to use the following code:

\usepackage{biblatex}
\addbibresource{example.bib}

%citations: 

\parencite[][]{author_title_date}

\cite %—the most basic one. Prints without any brackets except when using the alphabetic or numeric style when it uses square brackets;
\parencite %—prints citations in parentheses except when using the alphabetic or numeric style when it uses square brackets;
\footcite %—puts the citation in a footnote.

%Print bibliography (citations must be used in the document in order for the bibliography to be shown)
\printbibliography

Example 2: bibiitem latex

\begin{thebibliography}{9}
\bibitem{latexcompanion} 
Michel Goossens, Frank Mittelbach, and Alexander Samarin. 
\textit{The \LaTeX\ Companion}. 
Addison-Wesley, Reading, Massachusetts, 1993.

\bibitem{einstein} 
Albert Einstein. 
\textit{Zur Elektrodynamik bewegter K{\"o}rper}. (German) 
[\textit{On the electrodynamics of moving bodies}]. 
Annalen der Physik, 322(10):891–921, 1905.

\bibitem{knuthwebsite} 
Knuth: Computers and Typesetting,
\\\texttt{http://www-cs-faculty.stanford.edu/\~{}uno/abcde.html}
\end{thebibliography}