diff --git a/torchtext/csrc/bert_tokenizer.cpp b/torchtext/csrc/bert_tokenizer.cpp
index 06aba8ae7c..4bade1153a 100644
--- a/torchtext/csrc/bert_tokenizer.cpp
+++ b/torchtext/csrc/bert_tokenizer.cpp
@@ -1,3 +1,25 @@
+/* Portions Copyright (c) Meta Platforms, Inc. and affiliates.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+
+
+Original code is taken from
+https://github.com/LieluoboAi/radish/blob/master/radish/bert/bert_tokenizer.cc
+
+The code is modified and summary is provided in this PR
+https://github.com/pytorch/text/pull/1707
+*/
+
 #include <torchtext/csrc/bert_tokenizer.h>
 #include <utf8proc.h>