University of Mining and Geology, Studentski Grad, Prof. Boyan Kamenov Str., 1700 Sofia, Bulgaria; Geological Institute, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., Bl. 24, 1113 Sofia, Bulgaria
University of Mining and Geology “St Ivan Rilski”, Department of Geology and Geoinformatics, 1 Prof. Boyan Kamenov Str., Studentski Grad, 1700 Sofia, Bulgaria
University of Mining and Geology “St Ivan Rilski”, Department of Geology and Geoinformatics, 1 Prof. Boyan Kamenov Str., Studentski Grad, 1700 Sofia, Bulgaria
University of Mining and Geology “St Ivan Rilski”, Department of Geology and Geoinformatics, 1 Prof. Boyan Kamenov Str., Studentski Grad, 1700 Sofia, Bulgaria
University of Mining and Geology “St Ivan Rilski”, Department of Geology and Geoinformatics, 1 Prof. Boyan Kamenov Str., Studentski Grad, 1700 Sofia, Bulgaria
University of Mining and Geology “St Ivan Rilski”, Department of Geology and Geoinformatics, 1 Prof. Boyan Kamenov Str., Studentski Grad, 1700 Sofia, Bulgaria