Georgiev, Marin, Maria Baltadjieva, Bogdan Goranov, Mariya Brazkova, & Albert Krastanov. " Investigation of the probiotic properties and the acid production rate of strains Lactobacillus delbrueckii ssp. Bulgaricus." Food Science and Applied Biotechnology [Online], 2.2 (2019): 149-158. Web. 7 Apr. 2020