def _extract_citing_pmcids(self, page):
        if (not "PubMedToPMCcitingformSET" in page):
            raise ProviderContentMalformedError()
        dict_of_keylists = {"pubmed:pmc_citations": ["PubMedToPMCcitingformSET", "REFORM"]}
        (doc, lookup_function) = provider._get_doc_from_xml(page)
        try:
            pmcid_doms = doc.getElementsByTagName("PMCID")
            pmcids = [pmcid_dom.firstChild.data for pmcid_dom in pmcid_doms]
        except __HOLE__:
            logger.warning(u"%20s no PMCID xml tags for %s" % (self.provider_name, id))            
            pmcids = []
        return pmcids

    # documentation for pubmedtopmcciting: http://www.pubmedcentral.nih.gov/utils/entrez2pmcciting.cgi
    # could take multiple PMC IDs
dataset/ETHPy150Open Impactstory/total-impact-webapp/totalimpact/providers/pubmed.py/Pubmed._extract_citing_pmcids