1. 1999/30/EC (1999). Council Directive 1999/30/EC of 22 April 1999 relating to limit values for sulphur dioxide, nitrogen dioxide and oxides of nitrogen, particulate matter and lead in ambient air (The First Daughter Directive). From the Official Journal of the European Communities, 29.6.1999, En Series, L163/41.
2. 2004/107/EC (2004). Council Directive 2004/107/EC of 15 December 2004 relating to arsenic, cadmium, mercury, nickel and polycyclic aromatic hydrocarbons in ambient air. From the Official of the European Communities En Series, L 23. 26/1/2005
3. Alshibli, K. A., Asce, M., Alsaleh, M. I., & Asce, A. M. (2004). Characterizing surface roughness and shape of sands using digital microscopy. Journal of Computing in Civil Engineering, 18, 36–45.
4. Brenig, L., & Offer, Z. (2001). Airbone particles dynamics: towards a theoretical approach. Environmental Modeling and Assessment, 6, 1–5.
5. Campos-Ramos, A., Aragón-Piña, A., Galindo-Estrada, I., Querol, X., & Alastuey, A. (2009). Characterization of atmospheric aerosols by SEM in a rural area in the western part of México and its relation with different pollution sources. Atmospheric Environment, 43, 6159–6167.