J. L. Valverde, J. Lobato, I. Fernández, L. Marijuán, S. Pérez-Mohedano, and R. Talero, “Ferrous sulphate mono and heptahydrate reduction of hexavalent chromium in cement: effectiveness and storability”, Mater. constr., vol. 55, no. 279, pp. 39–52, Sep. 2005.