diff --git a/src/Phpml/Classifier/SupportVectorMachine.php b/src/Phpml/Classifier/SupportVectorMachine.php
index e16ebbe..8ee3731 100644
--- a/src/Phpml/Classifier/SupportVectorMachine.php
+++ b/src/Phpml/Classifier/SupportVectorMachine.php
@@ -34,9 +34,9 @@ class SupportVectorMachine implements Classifier
 
     /**
      * @param Kernel $kernel
-     * @param float $C
-     * @param float $tolerance
-     * @param int $upperBound
+     * @param float  $C
+     * @param float  $tolerance
+     * @param int    $upperBound
      */
     public function __construct(Kernel $kernel = null, float $C = 1.0, float $tolerance = .001, int $upperBound = 100)
     {
diff --git a/src/Phpml/Math/Kernel.php b/src/Phpml/Math/Kernel.php
index 776f78c..953a5fa 100644
--- a/src/Phpml/Math/Kernel.php
+++ b/src/Phpml/Math/Kernel.php
@@ -1,11 +1,11 @@
 <?php
-declare(strict_types = 1);
+
+declare (strict_types = 1);
 
 namespace Phpml\Math;
 
 interface Kernel
 {
-
     /**
      * @param float $a
      * @param float $b
@@ -13,5 +13,4 @@ interface Kernel
      * @return float
      */
     public function compute($a, $b);
-
 }
diff --git a/src/Phpml/Math/Kernel/RBF.php b/src/Phpml/Math/Kernel/RBF.php
index 4c7ecf1..5e77681 100644
--- a/src/Phpml/Math/Kernel/RBF.php
+++ b/src/Phpml/Math/Kernel/RBF.php
@@ -1,5 +1,6 @@
 <?php
-declare(strict_types = 1);
+
+declare (strict_types = 1);
 
 namespace Phpml\Math\Kernel;
 
@@ -35,5 +36,4 @@ class RBF implements Kernel
 
         return $result;
     }
-
 }
diff --git a/src/Phpml/Math/Product.php b/src/Phpml/Math/Product.php
index 3772207..70accb9 100644
--- a/src/Phpml/Math/Product.php
+++ b/src/Phpml/Math/Product.php
@@ -1,11 +1,11 @@
 <?php
-declare(strict_types = 1);
+
+declare (strict_types = 1);
 
 namespace Phpml\Math;
 
 class Product
 {
-
     /**
      * @param array $a
      * @param array $b
@@ -21,5 +21,4 @@ class Product
 
         return $product;
     }
-
 }
diff --git a/src/Phpml/Regression/LeastSquares.php b/src/Phpml/Regression/LeastSquares.php
new file mode 100644
index 0000000..22b254a
--- /dev/null
+++ b/src/Phpml/Regression/LeastSquares.php
@@ -0,0 +1,37 @@
+<?php
+
+declare (strict_types = 1);
+
+namespace Phpml\Regression;
+
+class LeastSquares implements Regression
+{
+    /**
+     * @var array
+     */
+    private $features;
+
+    /**
+     * @var array
+     */
+    private $targets;
+
+    /**
+     * @param array $features
+     * @param array $targets
+     */
+    public function train(array $features, array $targets)
+    {
+        $this->features = $features;
+        $this->targets = $targets;
+    }
+
+    /**
+     * @param array $features
+     *
+     * @return mixed
+     */
+    public function predict(array $features)
+    {
+    }
+}
diff --git a/src/Phpml/Regression/Regression.php b/src/Phpml/Regression/Regression.php
new file mode 100644
index 0000000..34e0b6d
--- /dev/null
+++ b/src/Phpml/Regression/Regression.php
@@ -0,0 +1,21 @@
+<?php
+
+declare (strict_types = 1);
+
+namespace Phpml\Regression;
+
+interface Regression
+{
+    /**
+     * @param array $features
+     * @param array $targets
+     */
+    public function train(array $features, array $targets);
+
+    /**
+     * @param array $features
+     *
+     * @return mixed
+     */
+    public function predict(array $features);
+}
diff --git a/tests/Phpml/Math/Kernel/RBFTest.php b/tests/Phpml/Math/Kernel/RBFTest.php
index cc22229..5b9bcb4 100644
--- a/tests/Phpml/Math/Kernel/RBFTest.php
+++ b/tests/Phpml/Math/Kernel/RBFTest.php
@@ -1,5 +1,6 @@
 <?php
-declare(strict_types = 1);
+
+declare (strict_types = 1);
 
 namespace test\Phpml\Math\Kernel;
 
@@ -7,7 +8,6 @@ use Phpml\Math\Kernel\RBF;
 
 class RBFTest extends \PHPUnit_Framework_TestCase
 {
-
     public function testComputeRBFKernelFunction()
     {
         $rbf = new RBF($gamma = 0.001);
@@ -22,5 +22,4 @@ class RBFTest extends \PHPUnit_Framework_TestCase
         $this->assertEquals(0.00451, $rbf->compute([1, 2, 3], [4, 5, 6]), '', $delta = 0.0001);
         $this->assertEquals(0, $rbf->compute([4, 5], [1, 100]));
     }
-
 }
diff --git a/tests/Phpml/Math/ProductTest.php b/tests/Phpml/Math/ProductTest.php
index ade9942..aba0ff2 100644
--- a/tests/Phpml/Math/ProductTest.php
+++ b/tests/Phpml/Math/ProductTest.php
@@ -1,5 +1,6 @@
 <?php
-declare(strict_types = 1);
+
+declare (strict_types = 1);
 
 namespace tests\Phpml\Math;
 
@@ -7,12 +8,10 @@ use Phpml\Math\Product;
 
 class ProductTest extends \PHPUnit_Framework_TestCase
 {
-
     public function testScalarProduct()
     {
         $this->assertEquals(10, Product::scalar([2, 3], [-1, 4]));
         $this->assertEquals(-0.1, Product::scalar([1, 4, 1], [-2, 0.5, -0.1]));
         $this->assertEquals(8, Product::scalar([2], [4]));
     }
-
-}
\ No newline at end of file
+}