diff --git a/ppocr/losses/ace_loss.py b/ppocr/losses/ace_loss.py
index bf15f8e3a7b355bd9e8b69435a5dae01fc75a892..915b99e6ec1d6cb4641d8032fa188c61006dfbb3 100644
--- a/ppocr/losses/ace_loss.py
+++ b/ppocr/losses/ace_loss.py
@@ -11,6 +11,9 @@
 # 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.
+
+# This code is refer from: https://github.com/viig99/LS-ACELoss
+
 from __future__ import absolute_import
 from __future__ import division
 from __future__ import print_function
@@ -32,7 +35,7 @@ class ACELoss(nn.Layer):
     def __call__(self, predicts, batch):
         if isinstance(predicts, (list, tuple)):
             predicts = predicts[-1]
-            
+
         B, N = predicts.shape[:2]
         div = paddle.to_tensor([N]).astype('float32')
 
diff --git a/ppocr/losses/center_loss.py b/ppocr/losses/center_loss.py
index cbef4df965e2659c6aa63c0c69cd8798143df485..f8c57fdd5c9b3f0dec5c3d0a811e5532abd2e45a 100644
--- a/ppocr/losses/center_loss.py
+++ b/ppocr/losses/center_loss.py
@@ -12,6 +12,8 @@
 #See the License for the specific language governing permissions and
 #limitations under the License.
 
+# This code is refer from: https://github.com/KaiyangZhou/pytorch-center-loss
+
 from __future__ import absolute_import
 from __future__ import division
 from __future__ import print_function
@@ -27,6 +29,7 @@ class CenterLoss(nn.Layer):
     """
     Reference: Wen et al. A Discriminative Feature Learning Approach for Deep Face Recognition. ECCV 2016.
     """
+
     def __init__(self,
                  num_classes=6625,
                  feat_dim=96,
diff --git a/ppocr/modeling/backbones/rec_mv1_enhance.py b/ppocr/modeling/backbones/rec_mv1_enhance.py
index 04a909b8ccafd8e62f9a7076c7dedf63ff745303..d8a7f4b5646eb70b5202aa3b3ac6494318b424ad 100644
--- a/ppocr/modeling/backbones/rec_mv1_enhance.py
+++ b/ppocr/modeling/backbones/rec_mv1_enhance.py
@@ -12,6 +12,8 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+# This code is refer from: https://github.com/PaddlePaddle/PaddleClas/blob/develop/ppcls/arch/backbone/legendary_models/pp_lcnet.py
+
 from __future__ import absolute_import
 from __future__ import division
 from __future__ import print_function