This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License.
Svetla Stankova
„Konstantin Preslavski” University of Shumen,
Faculty of Natural Sciences, Department of Geography and Regional DevelopmentShumen
Tzanko Tzankov
South-West University „Neofit Rilski” – Blagoevgrad,
Faculty of Mathematics and Natural Sciences, Department of Geography, Ecology and Environment ProtectionBlagoevgrad
Rosen Iliev
South-West University „Neofit Rilski” – Blagoevgrad,
Faculty of Mathematics and Natural Sciences, Department of Geography, Ecology and Environment ProtectionBlagoevgrad