Laravel：将自定义类导入迁移文件

I tried to import the class as in this article has been explained (method 3):

database/migrations/****_createOrdersTable.php

use Illuminate\Support\Facades\Schema;
use Illuminate\Database\Schema\Blueprint;
use Illuminate\Database\Migrations\Migration;

use App\Extenders\References;

class CreateOrdersTable extends Migration {
// ...
}

I got the error

  [Symfony\Component\Debug\Exception\FatalThrowableError]
  Class 'App\Extenders\References' not found

composer dump-autoload was not help.

I just forgot to declare namespace in References class:

namespace App\Extenders;