diff --git a/stats/percentile.go b/stats/percentile.go
index 3f06d52..5e1c13f 100644
--- a/stats/percentile.go
+++ b/stats/percentile.go
@@ -1,3 +1,7 @@
+// Copyright 2014 The Chihaya Authors. All rights reserved.
+// Use of this source code is governed by the BSD 2-Clause license,
+// which can be found in the LICENSE file.
+
 package stats
 
 import (
diff --git a/stats/percentile_test.go b/stats/percentile_test.go
index 569f051..66594fc 100644
--- a/stats/percentile_test.go
+++ b/stats/percentile_test.go
@@ -1,3 +1,7 @@
+// Copyright 2014 The Chihaya Authors. All rights reserved.
+// Use of this source code is governed by the BSD 2-Clause license,
+// which can be found in the LICENSE file.
+
 package stats
 
 import (