public function addEmails( $bookId, $emails ) {
        if( empty( $bookId ) || empty( $emails ) ) {
            return $this->handleError( 'Empty book id or emails' );
        }

        $data = array(
            'emails' => serialize( $emails )
        );

        $requestResult = $this->sendRequest( 'addressbooks/' . $bookId . '/emails', 'POST', $data );

        return $this->handleResult( $requestResult );
    }