diff --git a/inc/MicroBitI2C.h b/inc/MicroBitI2C.h
index 07ad607..0081205 100644
--- a/inc/MicroBitI2C.h
+++ b/inc/MicroBitI2C.h
@@ -10,6 +10,12 @@
   *
   * Presents a wrapped mbed call to capture failed I2C operations caused by a known silicon bug in the nrf51822.
   * Attempts to automatically reset and restart the I2C hardware if this case is detected.
+  * 
+  * For reference see PAN56 in: 
+  * 
+  * https://www.nordicsemi.com/eng/nordic/Products/nRF51822/PAN-nRF51822/24634
+  * 
+  * v2.0 through to v2.4
   */
 class MicroBitI2C : public I2C
 {