diff --git a/AppNotes.md b/AppNotes.md
index 097d679..d86f675 100644
--- a/AppNotes.md
+++ b/AppNotes.md
@@ -3,4 +3,5 @@
     1. [Reading List](http://readingjimwilliams.blogspot.com/p/best-app-notes.html)
     2. [AN47FA: High Speed Amplifier Techniques, A Designer’s Companion for Wideband Circuitry](https://www.analog.com/media/en/technical-documentation/application-notes/an47fa.pdf)
 2. [Unitrode Design Handbook](https://www.ti.com/seclit/ml/slup132/slup132.pdf)
-3. [TI Power Supply Design Seminars](https://www.ti.com/design-resources/seminars/power-supply-design-seminar-psds/psds-resources.html)
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+3. [TI Power Supply Design Seminars](https://www.ti.com/design-resources/seminars/power-supply-design-seminar-psds/psds-resources.html)
+4. [Power Supply Design Resource Center Group on Fcebook (Moderated? by Ray Ridley)](https://www.facebook.com/groups/1879510808953399)
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