link in the titlepage

frames.tex

@@ -2,12 +2,11 @@
 %\includeonlyframes{current}
 
 \begin{frame}
-   \tikz [remember picture,overlay]
-    \node at
-        ([yshift=1cm]current page.south)
-        %or: (current page.center)
-        {\includegraphics[height=.5cm]{by-sa}};
-  \titlepage
+   \begin{tikzpicture}[remember picture,overlay]
+     \node at ([yshift=1.5cm]current page.south) {\tiny\url{https://baltig.infn.it/giaco/cpp-memory-esc17}};
+     \node at ([yshift=1cm]current page.south) {\includegraphics[height=.5cm]{by-sa}};
+   \end{tikzpicture}
+   \titlepage
 \end{frame}
 
 \begin{frame}{Outline}