"Dmitry Fyodorovich Selivanov, (Дмитрий Фёдорович Селиванов, 17 February 1855, Gorodishche, Gorodishchensky District, Penza Oblast – 5 April 1932, Prague) was a Russian mathematician, known for his work on differential calculus and finite difference calculus." - (en.wikipedia.org 29.12.2020)