Stoyanov, P., R. Mladenov, I. Teneva, and D. Belkinova. “Study on Freshwater Algal Flora on the Territory of the Bulgarka Nature Park”. Journal of BioScience and Biotechnology, vol. 5, no. 2, Sept. 2016, pp. 129-37, https://editorial.uni-plovdiv.bg/index.php/JBB/article/view/29.