SGEM 2019 : 19th international multidisciplinary scientific geoconference SGEM 2019, 30 June - 6 July, 2019, Albena, Bulgaria. 19, 2. Hydrogeology, Engineering Geology and Geotechnics. 1st ed. Sofia : STEP92 Technology, 2019. 1171 s. Available on Internet: <http://dx.doi.org/10.5593/sgem2019/1.2> ISBN 978-619-7408-77-5.