[[l] Simeonova P, Lovchinov V. Introduction to Environmental Physics. Sofia: Avangard Prima, S; 2008. ISBN: 9789543233502.]Search in Google Scholar
[[2] Manahan SE. Environmental Chemistry. Boca Raton: Lewis Publishers/CRS Press; 2000. ISBN: 1566704928.]Search in Google Scholar
[[3] Cunningham WP, Saigo BW. Environmental Science, a Global Concern. New York: C. Brown/McGraw-Hill; 1998. ISBN: 9780071180726.]Search in Google Scholar
[[4] Alexander DE, Fairbridge RW, editors. Encyclopedia of Environmental Sciences. Hingam: Kluwer Academic Publishers; 1999. ISBN: 9781402044946.]Search in Google Scholar