diff --git a/ppdet/modeling/assigners/simota_assigner.py b/ppdet/modeling/assigners/simota_assigner.py
index eacd23022f1c95b05fad17c742932e8d80987324..ce22ad7e45f8a41c6ce1db1d97fea37bea6eb1d6 100644
--- a/ppdet/modeling/assigners/simota_assigner.py
+++ b/ppdet/modeling/assigners/simota_assigner.py
@@ -11,6 +11,10 @@
 # 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/open-mmlab/mmdetection/blob/master/mmdet/core/bbox/assigners/sim_ota_assigner.py
+"""
 
 import paddle
 import numpy as np
diff --git a/ppdet/modeling/necks/csp_pan.py b/ppdet/modeling/necks/csp_pan.py
index fccd25b754a9236a803a1f168b16ef204760efa5..6efbb15462b151eb750c802c1c71257741a3ce32 100644
--- a/ppdet/modeling/necks/csp_pan.py
+++ b/ppdet/modeling/necks/csp_pan.py
@@ -11,6 +11,10 @@
 # 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/open-mmlab/mmdetection/blob/master/mmdet/models/necks/yolox_pafpn.py
+"""
 
 import paddle
 import paddle.nn as nn