diff --git a/lectures/parallelism/slides.qmd b/lectures/parallelism/slides.qmd
index 99365a34c0052553c109c8384098e0e3471fb6e6..12b44d4fab6f4fb70cdadccaebefa5bb9f19222b 100644
--- a/lectures/parallelism/slides.qmd
+++ b/lectures/parallelism/slides.qmd
@@ -216,6 +216,9 @@ Starting with batter for $N$ pancakes and 1 pan, we can scale by using $P$ pans
     for (int i = 0; i < N; ++i)
         sum = sum + a[i];
 ```
+For other reduction operations see
+[OpenMP documentation](https://www.openmp.org/spec-html/5.1/openmpsu117.html#x152-1720002.21.5)
+
 
 # Doing stuff wrong
 ## What is going wrong here?