In memory of Ivan Petrovich Dolbnya

In the preface of the collected works of I. P. Dolbnya published in French by order of the Council of the Mining Institute of Empress Catherine II under the title “Oeuvres mathematiques de Jean Dolbnia,” the famous French mathematician Gaston Darboux said, in particular: ""... Most of his works were published in French in the Recueils des mathematiques and mainly in the Bulletin des sciemes mathematiques. By deciding to compare them in volume and present them as a single whole, the Mining School provided a real service to mathematical research. Dolbnya's work is a credit to his country.