^Drey, Victoria (18 April 2018). "Want to feel like a Ukrainian? Drink Ryazhenka before going to bed!". Russia Beyond. Retrieved 31 July 2020. Nobody knows for sure when and who firstly came up with this unique recipe, but originally it was invented in Ukraine and then spread all over the Slavic region. In Ancient Rus they mixed milk with cream in special earthen pots and left them in a stove for hours on low heat until ryazhenka thickened enough.
^Ken Albala, ed. (2011). Food Cultures of the World Encyclopedia. Vol. 1. ABC-CLIO. p. 382. ISBN9780313376269.
^А. И. Титюнник; Ю. М. Новоженов (1977). Советская национальная и зарубежная кухня. Москва: Высшая школа. ISBN9785458259040. [A. I. Tityunnik; Yu. M. Novozhenov (1977). Soviet ethnic and foreign cuisine (in Russian). Moscow: Vysshaya Shkola.]