SGEM SGEM 2019. 19th international multidisciplinary scientific geoconference. Vol. 19. Ecology, economics,education and legislation Issue: 5.3 Albena, 28.6.-7.7.2019 / rec. Harald Schuh, Michael Sideris. -- 1. vyd. -- Wien SGEM world science 2019. -- 591 s. -- ISBN : 978-619-7408-86-7. -- 10.5593/sgem2019/5.3. Schuh, Harald. Sideris, Michael