diff --git a/src/main/scala/uk/ac/soton/ecs/can/core/Adder.scala b/src/main/scala/uk/ac/soton/ecs/can/core/Adder.scala
index d29dd8eac67d4dd25748f0e1795059345cf889b5..87049e8463588fbe57f23c967d228c1cb1f364ce 100644
--- a/src/main/scala/uk/ac/soton/ecs/can/core/Adder.scala
+++ b/src/main/scala/uk/ac/soton/ecs/can/core/Adder.scala
@@ -1,3 +1,6 @@
+// SPDX-FileCopyrightText: 2021 Minyong Li <ml10g20@soton.ac.uk>
+// SPDX-License-Identifier: CERN-OHL-W-2.0
+
 package uk.ac.soton.ecs.can.core
 
 import chisel3._
diff --git a/src/main/scala/uk/ac/soton/ecs/can/core/Xorer.scala b/src/main/scala/uk/ac/soton/ecs/can/core/Xorer.scala
index e553a6a1b7bfccbdbdc94802a01c6f6c31db946f..d0824752a7157031d631bc7c6870dcaa428e7c86 100644
--- a/src/main/scala/uk/ac/soton/ecs/can/core/Xorer.scala
+++ b/src/main/scala/uk/ac/soton/ecs/can/core/Xorer.scala
@@ -1,3 +1,6 @@
+// SPDX-FileCopyrightText: 2021 Minyong Li <ml10g20@soton.ac.uk>
+// SPDX-License-Identifier: CERN-OHL-W-2.0
+
 package uk.ac.soton.ecs.can.core
 
 import chisel3._
diff --git a/src/test/scala/uk/ac/soton/ecs/can/core/AdderTest.scala b/src/test/scala/uk/ac/soton/ecs/can/core/AdderTest.scala
index d90ada8bd94bf0521b25410905ae0cafb64bb00a..6fe7840c7bbaef5a4d76ac07d33ee8a2fc8964db 100644
--- a/src/test/scala/uk/ac/soton/ecs/can/core/AdderTest.scala
+++ b/src/test/scala/uk/ac/soton/ecs/can/core/AdderTest.scala
@@ -1,3 +1,6 @@
+// SPDX-FileCopyrightText: 2021 Minyong Li <ml10g20@soton.ac.uk>
+// SPDX-License-Identifier: GPL-3.0-or-later
+
 package uk.ac.soton.ecs.can.core
 
 import org.scalatest._
diff --git a/src/test/scala/uk/ac/soton/ecs/can/core/XorerTest.scala b/src/test/scala/uk/ac/soton/ecs/can/core/XorerTest.scala
index b37df1cbdd2da8096eebddb7df518283b5fb1990..e0e36e6c019b49fa2b574b9df3d60f14516b8e6e 100644
--- a/src/test/scala/uk/ac/soton/ecs/can/core/XorerTest.scala
+++ b/src/test/scala/uk/ac/soton/ecs/can/core/XorerTest.scala
@@ -1,3 +1,6 @@
+// SPDX-FileCopyrightText: 2021 Minyong Li <ml10g20@soton.ac.uk>
+// SPDX-License-Identifier: GPL-3.0-or-later
+
 package uk.ac.soton.ecs.can.core
 
 import org.scalatest._