Article snapshot taken from Wikipedia with creative commons attribution-sharealike license.
Give it a read and then ask your questions in the chat.
We can research this topic together.
List of Compositions by Vladislav Blazhevich
Vladislav Blazhevich had no formal opus number system for his compositions. Many of Blazhevich's compositions either have vague date ranges, or no date at all. During his lifetime, his more popular music was published by Muzgiz (State Music Publishing House). Muzgiz used a system of plate numbers following the format M. ##### Г. from 1918-1964. For Blazhevich's more popular works, published with a plate number between 1918-1964, the number can be used to approximate the period which the composition is from, though note some plate numbers are far greater due to second and third republications decades after the initial one. Some dates can be found on Blazhevich's original manuscripts, or in his books Methods (1941) and Autobiography (1939). Some of his works' dates can be approximated due to their mention in his writings, necessitating them to have been written before that particular entry. For Blazhevich's more obscure works, such as Concerti No. 11, 12 and 13, they exist only in handwritten manuscript form, meaning their date of creation will never be known accurately. Further complicating matters, much of Blazhevich's content has been published illegally, for example Editions BIM's 1996 publication of Concerto No. 1, further confusing which works were written when. Nevertheless, most of Blazhevich's works can be dated within ~10 years, and his pedagogical publications as well as their edits and republications are all dated meticulously.
By genre
Trombone concerti
Concerto No. 1 in Eb Major (c. 1920-1930, likely around 1925) M. 14081 Г.