diff --git a/src/PIL/ImageFilter.py b/src/PIL/ImageFilter.py
index 562e19229..d2ece3752 100644
--- a/src/PIL/ImageFilter.py
+++ b/src/PIL/ImageFilter.py
@@ -149,8 +149,9 @@ class ModeFilter(Filter):
 
 
 class GaussianBlur(MultibandFilter):
-    """Blurs the image with an extended box filter, which approximates a
-    Gaussian kernel.
+    """Blurs the image with a sequence of extended box filters, which
+    approximates a Gaussian kernel. For details on accuracy see
+    <https://www.mia.uni-saarland.de/Publications/gwosdek-ssvm11.pdf>
 
     :param radius: Standard deviation of the Gaussian kernel.
     """