Jelev G, Stefanova D, Stefanov P, Bonev D, Stoyanova A, Chilakova D. GIS research project on karst in Bulgaria. ANSD [Internet]. 2021 Apr. 16 [cited 2024 Apr. 19];5:52-8. Available from: https://ojs.nbu.bg/index.php/ANSD/article/view/507