Remove the reference from the titlepage and move it to the Sources slide

VL1.tex

@@ -58,15 +58,6 @@
 
 \begin{document}
 
-% redefinition of author, fails before document env
-\author{
-\begin{tabular}{r@{ }l}
-Author: & Julian Ospald \\[1ex]
-Parts stolen from: & Brent Yorgey\\
-& (link at the end of the document)
-\end{tabular}
-}
-
 \frame{\titlepage}
 
 \begin{frame}
@@ -432,4 +423,15 @@ For haskell IDEs, see \url{https://wiki.haskell.org/IDEs}
 
 \end{frame}
 
+\begin{frame}
+\frametitle{Sources}
+\begin{itemize}
+\item much content was borrowed or is based on the haskell course from Brent Yorgey:\\ \url{https://www.seas.upenn.edu/~cis194/fall14/spring13/lectures.html}
+\item a few small pieces from the LYAH book \url{http://learnyouahaskell.com}
+\item general information from wikipedia: \\ \url{https://en.wikipedia.org}
+\item general information from haskell wiki: \\ \url{https://wiki.haskell.org}
+\end{itemize}
+
+\end{frame}
+
 \end{document}