Abstract
The accuracy of any historical research depends on independent verification of the related data and the completeness of available sources. According to nineteenth-century French historians, "Documents make History", which means that all available written sources are equally important for solving a particular task. In this aspect, classification of historical sources can be of great help. Like any classification, it groups its objects according to the presence or absence of an essential feature. Perhaps, the most famous methodological school was founded in Novosibirsk by S. S. Rozova, who dealt with issues of scientific classification. In the modern domestic tradition of the historical methodology, classification of historical sources is one of the most important research steps. It allows historians to give a genuine scientific character to their studies. However, classification of sources is not a mechanical action. As a creative process, it leads to variability. The present article introduces a comparative analysis of two classifications of historical sources on the history of Yakutia, which belonged to N. N. Ogloblin and V. F. Ivanov. N. N. Ogloblin created a detailed classification of sources, which covers the main groups of customs documentation. However, his second volume was found lacking.