The collection continues the tradition of publishing written sources that form the basis of the spiritual heritage of the Tatar people; acquaintance of readers with the latest research in the study of Tatar texts. The twelfth issue of the series includes the most important texts closely related to the history and culture of the Volga Bulgaria, which undoubtedly belong to the "golden fund" of the Tatar spiritual and written heritage. The project was implemented within the framework of the Main Action Plan for the preparation and holding of the celebration in 2022 of the 1100th anniversary of the adoption of Islam by the Volga Bulgaria.