M. G. Dirodi and  G. Gugliotta and  C. Leonardi,  Establishment of Air Quality Zones in Italy.   journal   = {International Journal of Environmental and Ecological Engineering}, [online]. World Academy of Science, Engineering and Technology.
    January 2015, vol. 98(2). 71 - 76
    [viewed 13 May 2021]. Available from: https://publications.waset.org/pdf/10000493.