how to add bibliography in latex code example

Example 1: 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}

Example 2: cite bibliography latex

//Build a bibliography
\begin{thebibliography}{99}

\markboth{ }{\textsl{Bibliography}}

\addcontentsline{toc}{chapter}{Bibliography}
\bibitem{A} Author, \emph{Title}.
\end{thebibliography}

//Cite somewhere in the text
...as cited in the book \cite{A}