Kostikova, V., A. Kuznetsov, V. Troshkina, and A. Belanova. “Morphological and Taxonomic Analysis of the Polymorphic Complex Spiraea Betulifolia ‒ Spiraea Beauverdiana in Russia”. Acta Biologica Sibirica, Vol. 5, no. 3, Sept. 2019, pp. 22-32, doi:10.14258/abs.v5.i3.6353.