References
- Toncheva, T., Nature utilization in tourism, Univ. ed. Economics, Sofia, 2009.
- Protected Areas Law, State Gazette, 133 of 11.11.1998, amendments and additions... 27 of 15.03.2013, 102 of 23.12.2022.
- http://e-ecodb.bas.bg/rdb/bg/vol2/4protected.html.
- http://www.helpos.com/archive/preview-web/12_033_12_index.html.
- Asenov, A., Biogeography and natural capital of Bulgaria. St. Kliment Ohridski University Publishing House, Sofia, 2021.
- Bachvarova, D., Biogeography of Bulgaria and conservation of biological diversity. University Publishing House Episkop Konstantin Preslavski, Shumen, 2017.
- Baikov, B., Ya. Naydenov, Ecology in tourism, ed. Forcom, Sofia, 2011.
- The source of the cited digital data is the official portal of the Association of Parks in Bulgaria – parks.bg.
- https://www.birdsinbulgaria.org/ovm.php?l=bg&pageNum_Ovm_All=0&totalRows_Ovm_All=114&id=53#
- Alexova, D., Sustainable development of Chiprovtsi municipality as a tourist destination. Tourism Brand Creation and Strategic Planning, ed. About the letters, Sofia, 2021.
- Mihailov, M., Sustainable development of tourism, NBU, Sofia, 2013.