diff --git a/src/synth/wavetable.h b/src/synth/wavetable.h
index 6b81576..be5ea37 100644
--- a/src/synth/wavetable.h
+++ b/src/synth/wavetable.h
@@ -15,6 +15,8 @@
 
 // see
 // https://jacajack.github.io/music/2019/12/10/PPG-EPROM.html
+// https://dbwbp.com/index.php/9-misc/37-synth-eprom-dumps
+
 
 // --------------------------------------------------------------
 // Types