diff --git a/pwm.md b/pwm.md
index 243b593..55bce23 100644
--- a/pwm.md
+++ b/pwm.md
@@ -6,7 +6,10 @@ The Raspberry Pi zero (1 and 2) have 2 PWM peripherals, allowing you to pulse pi
 # References
 - [Raspberry Pi Official Overlays information (github)](https://github.com/raspberrypi/firmware/blob/master/boot/overlays/README)
     - Line 4235 starts the description of the "pwm" overlay configuration
-- [Adafruit 2-channel PWM instructions](https://learn.adafruit.com/adding-basic-audio-ouput-to-raspberry-pi-zero/pi-zero-pwm-audio)
+- [Adding Basic Audio Ouput to Raspberry Pi Zero](https://learn.adafruit.com/adding-basic-audio-ouput-to-raspberry-pi-zero/pi-zero-pwm-audio)
+
+# Important Points
+1. The `gpio` program is no longer available.  It has been replaced with `pinctrl` which works a little differently.
 
 # Discussion