diff --git a/docs/images/wx_group.png b/docs/images/wx_group.png
index 61839efc4f0bd9bed39b919986db071261fb09a7..e65af8e60bb8ecf0e2adb83202b86e22456fba35 100644
Binary files a/docs/images/wx_group.png and b/docs/images/wx_group.png differ
diff --git a/ppcls/data/preprocess/batch_ops/batch_operators.py b/ppcls/data/preprocess/batch_ops/batch_operators.py
index 888f44c49ae23ed86af3942230914f13272d4d66..6f0abb864574f8bead1d1ad6461460b4ececc7a7 100644
--- a/ppcls/data/preprocess/batch_ops/batch_operators.py
+++ b/ppcls/data/preprocess/batch_ops/batch_operators.py
@@ -57,7 +57,10 @@ class BatchOperator(object):
 
 
 class MixupOperator(BatchOperator):
-    """ Mixup operator """
+    """ Mixup operator 
+    reference: https://arxiv.org/abs/1710.09412
+
+    """
 
     def __init__(self, class_num, alpha: float=1.):
         """Build Mixup operator
@@ -90,7 +93,10 @@ class MixupOperator(BatchOperator):
 
 
 class CutmixOperator(BatchOperator):
-    """ Cutmix operator """
+    """ Cutmix operator
+    reference: https://arxiv.org/abs/1905.04899
+
+    """
 
     def __init__(self, class_num, alpha=0.2):
         """Build Cutmix operator
@@ -146,7 +152,10 @@ class CutmixOperator(BatchOperator):
 
 
 class FmixOperator(BatchOperator):
-    """ Fmix operator """
+    """ Fmix operator 
+    reference: https://arxiv.org/abs/2002.12047
+    
+    """
 
     def __init__(self,
                  class_num,