diff --git a/glsl/WaveformPrimitives.glsl b/glsl/WaveformPrimitives.glsl
index 6d49b69..21e7a31 100644
--- a/glsl/WaveformPrimitives.glsl
+++ b/glsl/WaveformPrimitives.glsl
@@ -1,3 +1,5 @@
+// Available at https://www.shadertoy.com/view/clXSR7
+
 // COMMON
 
 // Sine wave. The constant here is Tau (2 * PI)