ARUKÜLA, Heino. EVALUATION AND STANDARDIZATION OF ESTONIAN OIL SHALE QUALITY CHARACTERISTICS. ENVIRONMENT. TECHNOLOGIES. RESOURCES. Proceedings of the International Scientific and Practical Conference, Rezekne, Latvia, v. 1, p. 47–55, 1997. DOI: 10.17770/etr1997vol1.1854. Disponível em: https://journals.ru.lv/index.php/ETR/article/view/1854.. Acesso em: 4 may. 2024.