[[1] Ion Untea (2010), Air Pollution Control-Politehnica Press Publishing House Bucharest]Search in Google Scholar
[[2] Virginia Ciobotariu, Ana Maria Socolescu (2008), Pollution and Environmental Protection-Bucharest Economic Publishing House]Search in Google Scholar
[[3] Daniela Ionela Ciolea (2012), Air Pollution-Universitas Petroşani Publishing House]Search in Google Scholar
[[4] Florian Dan, Carmen Eva Dan (2002), Environment Pollution Fuels-Dacia Publishing House Cluj Napoca- http://members.shaw.ca/james.case/lichens/biomonitoring.html;]Search in Google Scholar
[[5] Environmental Protection Agency, Preliminary Report on Ambient Air Quality for 2015, 2016, 2017 in Alba County;]Search in Google Scholar