@inproceedings{sgem2003paper,
  title = {TRACE ELEMENTS IN SULPHIDE AND SULPHATE MINERALS IN COAL AND THEIR ENVIRONMENTAL IMPACT},
  author = {I. Kostova},
  booktitle = {3rd International Scientific Conference - SGEM2003},
  year = {2003},
  pages = {27-28},
  publisher = {SGEM Scientific GeoConference},
  doi = {}
}