Link to Willi’s website instead of Youtube; add two PDFs from Johannes

resources/index.md

@@ -74,11 +74,18 @@ distributed with each Dynare release and also available here:
 </p>
 
 <p class="indent" markdown="1">
-<i class="fab fa-youtube"></i> Willi Mutschler’s video tutorials on how to use
-the parallel option in Dynare:
-[on Windows](https://www.youtube.com/watch?v=QKVm4bKTRbY),
-[on macOS](https://www.youtube.com/watch?v=yuB75NmE3Is),
-[on Ubuntu](https://www.youtube.com/watch?v=ei8MjNipUyU)
+<i class="fas fa-file-pdf"></i> [Johannes Pfeifer’s Guide to Specifying
+Observation Equations for the Estimation of DSGE
+Models](https://sites.google.com/site/pfeiferecon/Pfeifer_2013_Observation_Equations.pdf?attredirects=0)
+</p>
+
+<p class="indent" markdown="1">
+<i class="fas fa-file-pdf"></i> [Johannes Pfeifer’s Introduction to Graphs in Dynare](https://sites.google.com/site/pfeiferecon/Pfeifer_2014_Dynare_graphs.pdf?attredirects=0)
+</p>
+
+<p class="indent" markdown="1">
+<i class="fas fa-external-link-alt"></i> [Willi Mutschler’s tutorials, codes,
+teaching and research material](https://mutschler.eu/dynare/)
 </p>