public function toXML(DOMElement $parent) : DOMElement
    {
        Assert::notEmpty($this->OrganizationName);
        Assert::notEmpty($this->OrganizationDisplayName);
        Assert::notEmpty($this->OrganizationURL);

        $doc = $parent->ownerDocument;

        $e = $doc->createElementNS(Constants::NS_MD, 'md:Organization');
        $parent->appendChild($e);

        Extensions::addList($e, $this->Extensions);

        Utils::addStrings($e, Constants::NS_MD, 'md:OrganizationName', true, $this->OrganizationName);
        Utils::addStrings($e, Constants::NS_MD, 'md:OrganizationDisplayName', true, $this->OrganizationDisplayName);
        Utils::addStrings($e, Constants::NS_MD, 'md:OrganizationURL', true, $this->OrganizationURL);

        return $e;
    }