diff --git a/pngzop_references.html b/pngzop_references.html
index 9c13e98bd..f228bd6a8 100644
--- a/pngzop_references.html
+++ b/pngzop_references.html
@@ -6,6 +6,7 @@
 <a href="https://code.google.com/p/zopfli/downloads/detail?name=Data_compression_using_Zopfli.pdf&can=2&q=">
 Data_compression_using_Zopfli.pdf</a>
 <li><a href="http://zlib.net/pigz/">zlib.net/pigz</a> (parallel gzip)
+<li><a href="http://zlib.net/zlib/">zlib.net</a> (zlib/examples/zpipe.c)
 </ul>
 </body>
 </html>