[Nineteenth] 19th International Multidisciplinary Scientific GeoConference SGEM 2019: 30 June - 06 July, 2019 - Albena, Bulgaria : Conference Proceedings : Issue 5.3, Ecology, Economics, Education and Legislation. Sofia: STEF92 Technology Ltd.; 2019. p. XII, 960 p. ISBN: 978-619-7-408-86-7.