6.Feiz, R., Ammenberg, J., Baas, L., Eklund, M., Helgstrand, A., and Marshall, R.,
                           “Improving the CO2 Performance of Cement, Part I: Utilizing Life-Cycle Assessment
                           and Key Performance Indicators to Assess Development within the Cement Industry”,
                           Journal of Cleaner Production, 2014. DOI:10.1065/lca2007.05.327.
