Load up the citations, if present, for initializing with the Voevent.

def from_etree(root):
        """
        Load up the citations, if present, for initializing with the Voevent.
        """
        cite_list = []
        citations = root.xpath('Citations/EventIVORN')
        if citations:
            description = root.xpath('Citations/Description')
            if description:
                description_text = description[0].text
            else:
                description_text = None
            for entry in root.Citations.EventIVORN:
                if entry.text:
                    cite_list.append(
                        Cite(ref_ivorn=entry.text,
                             cite_type=entry.attrib['cite'],
                             description=description_text)
                    )
                else:
                    logger.info(
                        'Ignoring empty citation in {}'.format(
                            root.attrib['ivorn']))
        return cite_list