diff --git a/build/shared/examples/2.Digital/DigitalIputPullup/DigitalIputPullup.ino b/build/shared/examples/2.Digital/DigitalIputPullup/DigitalIputPullup.ino
index 99b5a5476..093304595 100644
--- a/build/shared/examples/2.Digital/DigitalIputPullup/DigitalIputPullup.ino
+++ b/build/shared/examples/2.Digital/DigitalIputPullup/DigitalIputPullup.ino
@@ -14,6 +14,8 @@
  created 14 March 2012
  by Scott Fitzgerald
  
+ http://www.arduino.cc/en/Tutorial/InputPullupSerial
+ 
  This example code is in the public domain
  
  */