• Black crusts removal: the effect of stone yellowing and cleaning strategies. Gaviño M.,  Castillejo M., Vergès-Belmin V., Nowik W., Oujja M., Rebollar E., Hermosin B., Saiz-Jimenez C. (2004). Air Pollution and Cultural Heritage, Ed C. Saiz-Jimenez, A. A. Balkema  Publishers, Leiden, The Netherlands, 239-245.