diff --git a/src/Avalonia.Base/Collections/Pooled/ClearMode.cs b/src/Avalonia.Base/Collections/Pooled/ClearMode.cs
index 6b6df303d4..d78ac8feab 100644
--- a/src/Avalonia.Base/Collections/Pooled/ClearMode.cs
+++ b/src/Avalonia.Base/Collections/Pooled/ClearMode.cs
@@ -1,4 +1,7 @@
-namespace Avalonia.Collections.Pooled
+// This source file is adapted from the Collections.Pooled.
+// (https://github.com/jtmueller/Collections.Pooled/tree/master/Collections.Pooled/)
+
+namespace Avalonia.Collections.Pooled
 {
     /// <summary>
     /// This enum allows control over how data is treated when internal
diff --git a/src/Avalonia.Base/Collections/Pooled/IReadOnlyPooledList.cs b/src/Avalonia.Base/Collections/Pooled/IReadOnlyPooledList.cs
index 1a947db4b7..9bc3609dc5 100644
--- a/src/Avalonia.Base/Collections/Pooled/IReadOnlyPooledList.cs
+++ b/src/Avalonia.Base/Collections/Pooled/IReadOnlyPooledList.cs
@@ -1,4 +1,7 @@
-using System;
+// This source file is adapted from the Collections.Pooled.
+// (https://github.com/jtmueller/Collections.Pooled/tree/master/Collections.Pooled/)
+
+using System;
 using System.Collections.Generic;
 
 namespace Avalonia.Collections.Pooled