@proceedings{sgem202142,
  title = {21st International Multidisciplinary Scientific GeoConference SGEM 2021, Energy and Clean Technologies, Vol. 21, Issue 4.2},
  author = {International authors},
  year = {2021},
  publisher = {STEF92 Technology},
  isbn = {},
  doi = {10.5593/sgem2021v/4.2}
}