Ivanova, Ekaterina, Boian Koulov, Bilyana Borisova, Assen Assenov, and Kiril Vassilev. “GIS-Based Valuation of Ecosystem Services in Mountain Regions: A Case Study of the Chepelare Municipality in Bulgaria”. European Journal of Sustainable Development 5, no. 4 (October 1, 2016): 335. Accessed December 22, 2024. https://ecsdev.org/ojs/index.php/ejsd/article/view/409.