bibTex simple example! [closed]

Question

I found this sample example im net. I created "references.bib" file in my template directory. I am getting the following output: Hallo world[einstein] with the warning: citation einstein on page 1 undefined

Do I miss something?

The contains of my references.bib is:

@artikel{einstein,
  author = {Albert Einstein},
  title = {the true about tree},
  journaltitle = {Annalen der Physik},
  year = {1905},
  volume = {322},
  number = {10},
  pages = {891-921}
} 


\documentclass{article}
\usepackage[backend=bibtex]{biblatex}
%\bibliography{references} 
%\addbibresource{<database>.<extension>}
\addbibresource{references.bib}
\begin{document}
Hallo world\cite{einstein}
\printbibliography
\end{document}

I appreciate any help.

Answer 1

Change @artikel to @article:

\documentclass{article}
\usepackage[hyperref=true,
    natbib=true,
    style=authortitle-dw,
    backend=biber]{biblatex}

\begin{filecontents}{\jobname.bib}
    @article{einstein,
        author = {Albert Einstein},
        title = {the true about tree},
        journaltitle = {Annalen der Physik},
        year = {1905},
        volume = {322},
        number = {10},
        pages = {891--921}
    }
\end{filecontents}
\addbibresource{\jobname.bib}

\begin{document}
    Hallo world \\
    \cite{einstein}
    \printbibliography
\end{document}