SGEM 2016 : 16th international multidisciplinary scientific geoconference SGEM 2016, 30. June - 6, July, 2016, Albena, Bulgaria. I. Ecology, economics, education and legislation, conference proceedings. 1st ed. Sofia : STEP92 Technology, 2016. 1023 s. Available on Internet: <http://www.sgem.org> ISBN 978-619-7105-65-0.