public static function create( $name = null, $conf = null ) 
	{
		if ( is_null( $name ) ) 
		{
			$name = static::$_default;
		}

		if ( !is_null( $conf ) && is_array( $conf ) )
		{
			return static::$_instances[$name] = new static( $name, $conf );
		}

		if ( !isset( static::$_instances[$name] ) )
		{
			static::$_instances[$name] = new static( $name );
		}

		return static::$_instances[$name];
	}