diff --git a/Program.cs b/Program.cs
index e2fcb59..2e5a3de 100644
--- a/Program.cs
+++ b/Program.cs
@@ -28,6 +28,8 @@ public class CameraInfo {
 }
 
 // FIXME: switch to immediate mode??
+// https://gamedev.stackexchange.com/questions/198805/opentk-immediate-mode-on-net-core-doesnt-work
+// https://www.youtube.com/watch?v=Q23Kf9QEaO4
 public class Shader : IDisposable {
   public int Handle;
   private bool init = false;