public function getFromSource( $key, $source, $strict = FALSE )
	{
		$data	= $this->getAllFromSource( $source );
		if( isset( $data[$key] ) )
			return $data[$key];
		if( !$strict )
			return NULL;
		throw new InvalidArgumentException( 'Invalid key "'.$key.'" in source "'.$source.'"' );
	}