diff --git a/stats/edm.go b/stats/edm.go
index 70e0c80..1533436 100644
--- a/stats/edm.go
+++ b/stats/edm.go
@@ -1,4 +1,4 @@
-// Copyright 2019 The Go Authors. All rights reserved.
+// Copyright 2021 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
@@ -18,7 +18,7 @@
 	ta, tb, tab *IntervalTree
 }
 
-// normalize normalizes an slice of floats in place.
+// normalize normalizes a slice of floats in place.
 func normalize(input []float64) []float64 {
 	// gracefully handle empty inputs.
 	if len(input) == 0 {
diff --git a/stats/edm_test.go b/stats/edm_test.go
index cfdfb8c..b21d9d9 100644
--- a/stats/edm_test.go
+++ b/stats/edm_test.go
@@ -1,4 +1,4 @@
-// Copyright 2019 The Go Authors. All rights reserved.
+// Copyright 2021 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
diff --git a/stats/edmx.go b/stats/edmx.go
index 59d91af..2e43d05 100644
--- a/stats/edmx.go
+++ b/stats/edmx.go
@@ -1,3 +1,7 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
 package stats
 
 import (
diff --git a/stats/itree.go b/stats/itree.go
index 7a79052..20ebc8e 100644
--- a/stats/itree.go
+++ b/stats/itree.go
@@ -1,10 +1,14 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
 package stats
 
 import (
 	"math"
 )
 
-// IntervalTree is a structure used to make caluclating running medians quick.
+// IntervalTree is a structure used to make a calculation of running medians quick.
 // The structure is described in the Section 8/Appendix of the paper.
 type IntervalTree struct {
 	d    int
diff --git a/stats/itree_test.go b/stats/itree_test.go
index cf79215..caf705a 100644
--- a/stats/itree_test.go
+++ b/stats/itree_test.go
@@ -1,3 +1,7 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
 package stats
 
 import (