Jančev, Simeon, AND Karamačoska, Biljana. " Mass-spectrometric examinations (δ34S) of different baryte, pyrite, galena, sphalerite samples from the ore occurrences in the mixed series at Nežilovo village, Macedonia" Acta Musei Macedonici Scientiarum Naturalium [Online], Volume 20 Number 1 (21 December 2017)