\documentclass{sp}
\usepackage{ngerman}
\usepackage{natbib}
\bibpunct[:]{(}{)}{,}{a}{}{,}
% The \pdf* commands provide metadata for the PDF output.
% Do not use LaTeX style / commands like \emph{} inside these.
\pdfauthor{Author Full Name(s)}
\pdftitle{Full title}
\pdfkeywords{keyword list, each, separated, by commas}

% Optional short title inside square brackets, for the running headers.
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\title{Hier eine schicke Überschrift}

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\author[dein Name]{% As many authors as you like, each separated by \AND.
  \spauthor{dein Name \\ \institute{Kursname, Institut, etc.}}}

  
\begin{document}

\maketitle


\section{Erste Referenz}

First paragraph \citep{sells_korean_1995}.\\
... nicht kanonische Umgebung \cite[Vgl.][]{sells_korean_1995}


\section{Zweite Referenz}

Second paragraph \citep[153-159, 168]{haider_syntax_2010}.\\
Haiders (\citeyear[5]{haider_syntax_2010}) Bemühungen ist es zu verdanken, dass...

\section{Dritte Referenz}

Third paragraph \citep{viesel_wer_2019}.\\
Der neuesten Litertur zu diesem Thema \citep{haider_syntax_2010, sells_korean_1995} ist zu entnehmen, dass...


\bibliography{bibfile} 
\bibliographystyle{sp_deutsch}


\end{document}
