diff --git a/documents/Programmierparadigmen/MPI.tex b/documents/Programmierparadigmen/MPI.tex
index d59f50d..6218247 100644
--- a/documents/Programmierparadigmen/MPI.tex
+++ b/documents/Programmierparadigmen/MPI.tex
@@ -19,6 +19,9 @@ Das wird \texttt{mpicc hello-world.c} kompiliert.\\
 Mit \texttt{mpirun -np 14 scripts/mpi/a.out} werden 14 Kopien des Programms
 gestartet.
 
+Hierbei ist \texttt{MPI\_COMM\_WORLD}\xindex{MPI\_COMM\_WORLD} der Standard-Kommunikator,
+der von \texttt{MPI\_Init} erstellt wird.
+
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 \section{MPI Datatypes}\xindex{MPI datatypes}
 
@@ -169,6 +172,9 @@ Verteilt Daten vom Prozess \texttt{root} unter alle anderen Prozesse in der Grup
 \inputminted[numbersep=5pt, tabsize=4]{c}{scripts/mpi/mpi-reduce-example.c}
 
 \section{Beispiele}
+
+\inputminted[numbersep=5pt, tabsize=4]{c}{scripts/mpi/mpi-sum-reduce.c}
+
 \section{Weitere Informationen}
 \begin{itemize}
     \item \url{http://mpitutorial.com/}
diff --git a/documents/Programmierparadigmen/Programmierparadigmen.pdf b/documents/Programmierparadigmen/Programmierparadigmen.pdf
index eab63ea..8900551 100644
Binary files a/documents/Programmierparadigmen/Programmierparadigmen.pdf and b/documents/Programmierparadigmen/Programmierparadigmen.pdf differ
diff --git a/documents/Programmierparadigmen/Readme.md b/documents/Programmierparadigmen/Readme.md
index 72b843e..7c3a510 100644
--- a/documents/Programmierparadigmen/Readme.md
+++ b/documents/Programmierparadigmen/Readme.md
@@ -1,3 +1,7 @@
 Dies ist ein **inoffizielles, von Studenten erstelltes Skript**
 zur Vorlesung "Programmierparadigmen" am KIT bei
 Herrn Prof. Dr. Snelting (WS 2013/2014).
+
+Docker
+------
+You might also be interested in the [programming paradigms docker project](https://github.com/kitedu/programming-paradigms).
\ No newline at end of file
diff --git a/documents/Programmierparadigmen/scripts/mpi/mpi-sum-reduce.c b/documents/Programmierparadigmen/scripts/mpi/mpi-sum-reduce.c
new file mode 100644
index 0000000..49550df
--- /dev/null
+++ b/documents/Programmierparadigmen/scripts/mpi/mpi-sum-reduce.c
@@ -0,0 +1,35 @@
+// Quelle: Klausur vom SS 2013 am KIT bei 
+// Prof. Dr.-Ing. Gregor Snelting
+void my_int_sum_reduce(int *sendbuf, 
+    int *recvbuf, int count,
+    int root, MPI_Comm comm)
+{
+    int size, rank;
+    MPI_Comm_size(comm, &size);
+    MPI_Comm_rank(comm, &rank);
+    if (rank == root) {
+        /* Initialize recvbuf with our own values. */
+        for (int i = 0; i < count; ++i) {
+            recvbuf[i] = sendbuf[i];
+        }
+
+        /* Receive values from every other node
+           and accumulate. */
+        for (int i = 0; i < size; ++i) {
+            if (i == root)
+                continue;
+
+            int other[count];
+            MPI_Recv(other, count, MPI_INT, 
+                i, 0, comm, MPI_STATUS_IGNORE);
+            
+            for (int j = 0; j < count; ++j) {
+                recvbuf[j] += other[j];
+            }
+        }
+    } else {
+        /* Send our values to root. */
+        MPI_Send(sendbuf, count, MPI_INT, 
+            root, 0, comm);
+    }
+}
\ No newline at end of file