High mountain treeless zone of the Central Balkan National Park : biological diversity and problems of its conservation
2000
Popov, Alexi |
Meshinev, Tenyo |
Bulgaria, Ministry of Environment and Waters
Biodiversity of the Srebarna biosphere reserve : checklist and bibliography
1998
Michev, T. |
Georgiev, B. B. |
Petrova, A. V. |
Stoyneva, M. P. |