diff --git a/TreeColumn.php b/TreeColumn.php
index 1ac814c..4b51e09 100644
--- a/TreeColumn.php
+++ b/TreeColumn.php
@@ -14,6 +14,7 @@
 
 /**
  * Column is the base class of all [[TreeGrid]] column classes.
+ * The code was based in: https://github.com/yiisoft/yii2/blob/master/framework/grid/DataColumn.php
  *
  * @author Leandro Gehlen <leandrogehlen@gmail.com>
  */
diff --git a/TreeGrid.php b/TreeGrid.php
index 1252dfe..e8740c6 100644
--- a/TreeGrid.php
+++ b/TreeGrid.php
@@ -14,6 +14,7 @@
 
 /**
  * TreeGrid renders a jQuery TreeGrid component.
+ * The code was based in: https://github.com/yiisoft/yii2/blob/master/framework/grid/GridView.php
  *
  * @see https://github.com/maxazan/jquery-treegrid
  * @author Leandro Gehlen <leandrogehlen@gmail.com>