<ref xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:mml="http://www.w3.org/1998/Math/MathML" id="R12"><label>12</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Ballester-Costa</surname><given-names>C</given-names></name><name><surname>Sendra</surname><given-names>E</given-names></name><name><surname>Fern&#225;ndez-L&#243;pez</surname><given-names>J</given-names></name><name><surname>P&#233;rez-&#193;lvarez</surname><given-names>JA</given-names></name><name><surname>Viuda-Martos</surname><given-names>M</given-names></name></person-group><article-title>Chemical composition and in vitro antibacterial properties of essential oils of four Thymus species from organic growth</article-title><source>Industrial Crops and Products</source><year>2013</year><volume>50</volume><fpage>304</fpage><lpage>311</lpage></element-citation></ref>