VALGMA, Ingo. MAPPING POTENTIAL AREAS OF GROUND SUBSIDENCE IN ESTONIAN UNDERGROUND OIL SHALE MINING DISTRICT. ENVIRONMENT. TECHNOLOGIES. RESOURCES. Proceedings of the International Scientific and Practical Conference, Rezekne, Latvia, v. 1, p. 227–232, 1999. DOI: 10.17770/etr1999vol1.1869. Disponível em: https://journals.rta.lv/index.php/ETR/article/view/1869.. Acesso em: 5 may. 2024.