diff --git a/CHANGELOG.md b/CHANGELOG.md
index 11b0807..7829691 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3,8 +3,13 @@ CHANGELOG
 
 This changelog references the relevant changes done in PHP-ML library.
 
-* 0.3.1 (in plan/progress)
-    * feature [Regression] - SSE, SSTo, SSR  - sum of the squared
+* 0.4.0 (2017-02-23)
+    * feature [Classification] - Ensemble Classifiers : Bagging and RandomForest by Mustafa Karabulut
+    * feature [Classification] - RandomForest::getFeatureImportances() method by Mustafa Karabulut
+    * feature [Classification] - Linear classifiers: Perceptron, Adaline, DecisionStump by Mustafa Karabulut
+    * feature [Classification] - AdaBoost algorithm by Mustafa Karabulut
+    * bug [Math] - Check if matrix is singular doing inverse by Povilas Susinskas
+    * optimization - Euclidean optimization by Mustafa Karabulut
 
 * 0.3.0 (2017-02-04)
     * feature [Persistency] - ModelManager - save and restore trained models by David Monllaó
diff --git a/README.md b/README.md
index 62a906d..c362a2c 100644
--- a/README.md
+++ b/README.md
@@ -56,6 +56,11 @@ Example scripts are available in a separate repository [php-ai/php-ml-examples](
     * Ensemble Algorithms
         * Bagging (Bootstrap Aggregating)
         * Random Forest
+        * AdaBoost
+    * Linear
+        * Adaline
+        * Decision Stump
+        * Perceptron
 * Regression
     * [Least Squares](http://php-ml.readthedocs.io/en/latest/machine-learning/regression/least-squares/)
     * [SVR](http://php-ml.readthedocs.io/en/latest/machine-learning/regression/svr/)
diff --git a/src/Phpml/Exception/MatrixException.php b/src/Phpml/Exception/MatrixException.php
index 2815804..1b01659 100644
--- a/src/Phpml/Exception/MatrixException.php
+++ b/src/Phpml/Exception/MatrixException.php
@@ -27,6 +27,6 @@ class MatrixException extends \Exception
      */
     public static function singularMatrix()
     {
-       return new self('Matrix is singular');
+        return new self('Matrix is singular');
     }
 }
diff --git a/tests/Phpml/Math/MatrixTest.php b/tests/Phpml/Math/MatrixTest.php
index 48a6fe9..0b46612 100644
--- a/tests/Phpml/Math/MatrixTest.php
+++ b/tests/Phpml/Math/MatrixTest.php
@@ -146,13 +146,13 @@ class MatrixTest extends TestCase
      */
     public function testThrowExceptionWhenInverseIfMatrixIsSingular()
     {
-       $matrix = new Matrix([
+        $matrix = new Matrix([
           [0, 0, 0],
           [0, 0, 0],
           [0, 0, 0],
        ]);
 
-       $matrix->inverse();
+        $matrix->inverse();
     }
 
     public function testInverseMatrix()