cite bibtex in overleaf code example

Example 1: 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}

Example 2: overleaf bibtex

@book{texbook,
  author = {Donald E. Knuth},
  year = {1986},
  title = {The \TeX{} Book},
  publisher = {Addison-Wesley Professional}
}

@book{latex:companion,
  author = {Frank Mittelbach and Michel Gossens
            and Johannes Braams and David Carlisle
            and Chris Rowley},
  year = {2004},
  title = {The \LaTeX{} Companion},
  publisher = {Addison-Wesley Professional},
  edition = {2}
}

@book{latex2e,
  author = {Leslie Lamport},
  year = {1994},
  title = {\LaTeX: a Document Preparation System},
  publisher = {Addison Wesley},
  address = {Massachusetts},
  edition = {2}
}

@article{knuth:1984,
  title={Literate Programming},
  author={Donald E. Knuth},
  journal={The Computer Journal},
  volume={27},
  number={2},
  pages={97--111},
  year={1984},
  publisher={Oxford University Press}
}

@inproceedings{lesk:1977,
  title={Computer Typesetting of Technical Journals on {UNIX}},
  author={Michael Lesk and Brian Kernighan},
  booktitle={Proceedings of American Federation of
             Information Processing Societies: 1977
             National Computer Conference},
  pages={879--888},
  year={1977},
  address={Dallas, Texas}
}