Center for the Study of Carbon Dioxide and Global Change. "The Influence of CO2 on Plant Antioxidants.” Last modified January 8, 2015. http://www.co2science.org/subject/a/summaries/antioxidants.php.
Center for the Study of Carbon Dioxide and Global Change. "The Global Medieval Warm Period.” Last modified October 30, 2014. http://www.co2science.org/subject/g/summaries/globalmwp.php.