<ref xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:mml="http://www.w3.org/1998/Math/MathML" id="R4"><label>4</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Rota</surname><given-names>MC</given-names></name><name><surname>Herrera</surname><given-names>A</given-names></name><name><surname>Mart&#237;nez</surname><given-names>RM</given-names></name><name><surname>Sotomayor</surname><given-names>JA</given-names></name><name><surname>Jord&#225;n</surname><given-names>MJ</given-names></name></person-group><article-title>Antimicrobial activity and chemical composition of Thymus vulgaris, Thymus zygis and Thymus hyemalis essential oils</article-title><source>Food Control</source><year>2008</year><volume>19</volume><issue>7</issue><fpage>681</fpage><lpage>687</lpage></element-citation></ref>