Install e-commerce sonata ERROR

I am trying to install sonata in my symfony project.

I am my composer .jso add:

"require": {
    "php": ">=5.3.3",
    "symfony/symfony": "2.6.*",
    "doctrine/orm": "~2.2,>=2.2.3",
    "doctrine/doctrine-bundle": "~1.2",
    "twig/extensions": "~1.0",
    "symfony/assetic-bundle": "~2.3",
    "symfony/swiftmailer-bundle": "~2.3",
    "symfony/monolog-bundle": "~2.4",
    "sensio/distribution-bundle": "~3.0",
    "sensio/framework-extra-bundle": "~3.0",
    "incenteev/composer-parameter-handler": "~2.0",
    "genemu/form-bundle": "2.2.*",
    "sonata-project/ecommerce": "2.3@dev"
},

      

        
        
        
      

    

I am doing the following command: composer update

Loading composer repositories with package information
Updating dependencies (including require-dev)
Your requirements could not be resolved to an installable set of packages.

  Problem 1
    - The requested package sonata-project/ecommerce could not be found in any version, there may be a typo in the package name.

Potential causes:
 - A typo in the package name
 - The package is not available in a stable-enough version according to your minimum-stability setting
   see <https://groups.google.com/d/topic/composer-dev/_g3ASeIFlrc/discussion> for more details.

Read <http://getcomposer.org/doc/articles/troubleshooting.md> for further common problems.

      

        
        
        
      

    

Does anyone know why?

Thank you Best wishes