The book for the first time publishes letters from the governor of the Kalmyk Khanate Ubashi to the Astrakhan provincial administration, written in the period from 1763 to 1769. Unique written monuments of the business language of the Kalmyks of the 18th century, stored in the National Archive of the Republic of Kalmykia, are put into circulation. The book is intended for specialists, teachers, graduate students, students and a wide range of readers interested in the evolution of the Kalmyk language and writing, as well as the history and culture of Kalmykia.